Q:

facet_grid weird rearrangement of values

I have this plot that I've generated using ggplot2 in R. 

The code that produces this plot is:
  plot <- ggplot(mockdata, aes(variable, Measurement)) + 
    geom_tile(aes(fill = mockdata$plotval), colour = "dark red")  + facet_grid(~type, scales='free', space='free') + scale_fill_gradient2(limits=c(-20, 20),high = "firebrick3", low = "dodgerblue4") + 
    theme_minimal() + theme(axis.text.x=element_text(size=28, angle=90), axis.text.y=element_text(size=28, face = "italic")) + 
    labs(title="", x="", y="", fill="") + theme(strip.text.x=element_blank(),strip.text.y=element_text(size=20, angle=0))

As you can see, I've added a horizontal space based on capitalization of my x-axis variables. Now however, I would like to also add vertical spacing based on another factor variable. I simply change the code to be:
ggplot(mockdata, aes(variable, Measurement)) + 
    geom_tile(aes(fill = mockdata$plotval), colour = "dark red")  + facet_grid(category~type, scales='free', space='free') + scale_fill_gradient2(limits=c(-20, 20),high = "firebrick3", low = "dodgerblue4") + 
    theme_minimal() + theme(axis.text.x=element_text(size=28, angle=90), axis.text.y=element_text(size=28, face = "italic")) + 
    labs(title="", x="", y="", fill="") + theme(strip.text.x=element_blank(),strip.text.y=element_text(size=20, angle=0))

The above gives exactly the look I'm going after but notice that the values are all messed up! For example 20:b and 20:c are blue in the first plot but red in the second plot. The first plot contains the correct values. 
I've been going crazy going over my factor labelling for hours but I can't seem to find the problem. I would like a solution as how I can add the vertical space to my first plot, using facet_grid or no, it doesn't matter, and special bonus points will be given to anyone who can explain what went wrong in my second plot. 
dput(mockdata)
structure(list(Measurement = structure(c(20L, 19L, 18L, 17L, 
16L, 15L, 14L, 13L, 12L, 11L, 10L, 9L, 8L, 7L, 6L, 5L, 4L, 3L, 
2L, 1L, 20L, 19L, 18L, 17L, 16L, 15L, 14L, 13L, 12L, 11L, 10L, 
9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L, 20L, 19L, 18L, 17L, 16L, 
15L, 14L, 13L, 12L, 11L, 10L, 9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 
1L, 20L, 19L, 18L, 17L, 16L, 15L, 14L, 13L, 12L, 11L, 10L, 9L, 
8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L, 20L, 19L, 18L, 17L, 16L, 15L, 
14L, 13L, 12L, 11L, 10L, 9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L, 
20L, 19L, 18L, 17L, 16L, 15L, 14L, 13L, 12L, 11L, 10L, 9L, 8L, 
7L, 6L, 5L, 4L, 3L, 2L, 1L, 20L, 19L, 18L, 17L, 16L, 15L, 14L, 
13L, 12L, 11L, 10L, 9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L, 20L, 
19L, 18L, 17L, 16L, 15L, 14L, 13L, 12L, 11L, 10L, 9L, 8L, 7L, 
6L, 5L, 4L, 3L, 2L, 1L, 20L, 19L, 18L, 17L, 16L, 15L, 14L, 13L, 
12L, 11L, 10L, 9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L), .Label = c("1", 
"2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", 
"14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", 
"25", "26", "27", "28", "29", "30", "31", "32", "33", "34", "35", 
"36", "37", "38", "39", "40", "41", "42"), class = "factor"), 
    category = structure(c(3L, 4L, 4L, 4L, 5L, 5L, 6L, 6L, 6L, 
    6L, 6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 8L, 3L, 4L, 4L, 4L, 
    5L, 5L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 
    8L, 3L, 4L, 4L, 4L, 5L, 5L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 7L, 
    7L, 7L, 7L, 7L, 7L, 8L, 3L, 4L, 4L, 4L, 5L, 5L, 6L, 6L, 6L, 
    6L, 6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 8L, 3L, 4L, 4L, 4L, 
    5L, 5L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 
    8L, 3L, 4L, 4L, 4L, 5L, 5L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 7L, 
    7L, 7L, 7L, 7L, 7L, 8L, 3L, 4L, 4L, 4L, 5L, 5L, 6L, 6L, 6L, 
    6L, 6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 8L, 3L, 4L, 4L, 4L, 
    5L, 5L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 
    8L, 3L, 4L, 4L, 4L, 5L, 5L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 7L, 
    7L, 7L, 7L, 7L, 7L, 8L), .Label = c("x1", "x2", "x3", "x4", 
    "x5", "x6", "x7", "x8", "x9"), class = "factor"), variable = structure(c(1L, 
    1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
    1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
    2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 
    3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 
    4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
    4L, 4L, 4L, 4L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 
    5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 6L, 6L, 6L, 6L, 6L, 6L, 
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    8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 9L, 9L, 9L, 9L, 9L, 9L, 
    9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L), .Label = c("A", 
    "B", "C", "a", "b", "c", "d", "e", "f"), class = "factor"), 
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    -3.50674897408984, 2.32878867454675, 6.08880231131442, 3.57649498051523, 
    1.47892563787053, 9.02328415005142, 2.20120062219246, 4.0819925875773, 
    3.71593452037349, -5.74412509417193, -2.89944564130995, 0.971689966478527, 
    -7.1470559653621, -5.72231869642199, -5.67972109772494, 2.8539446575791, 
    -2.71662233198973, -6.1103007681231, -0.763747253307228, 
    2.87054648892738, 0.430922536570879, 3.77693890461838, -6.50274699717143, 
    -4.91618826741447, -6.42941204883235, 0.748910833398874, 
    -1.70023246253767, -5.61791916284656, 8.58346572108797, 7.63434201313085, 
    9.07436311632148, 3.59282303012629, 5.9556117321782, 4.26938428807087, 
    0.254017783801932, -2.91898903187407, -6.79130924645919, 
    -3.44450755141886, -2.95362541370008, 2.30636810656965, 0.133066085813731, 
    -1.86629336596673, -5.44811521866938, 2.96581392463054, -5.14540146724019, 
    -4.27705097606589, -4.60146383671481, -4.06649255708194, 
    -0.720361250431011, 3.02166727906391, 0.154186465719317, 
    -6.57791669570072, -6.02051198354564, -5.797507843288, 3.24850317060798
    ), type = c("1", "1", "1", "1", "1", "1", "1", "1", "1", 
    "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", 
    "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", 
    "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", 
    "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", 
    "1", "1", "1", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", "2", 
    "2", "2", "2")), .Names = c("Measurement", "category", "variable", 
"Pval", "effect", "direction", "plotval", "type"), row.names = c(23L, 
24L, 25L, 26L, 27L, 28L, 29L, 30L, 31L, 32L, 33L, 34L, 35L, 36L, 
37L, 38L, 39L, 40L, 41L, 42L, 65L, 66L, 67L, 68L, 69L, 70L, 71L, 
72L, 73L, 74L, 75L, 76L, 77L, 78L, 79L, 80L, 81L, 82L, 83L, 84L, 
107L, 108L, 109L, 110L, 111L, 112L, 113L, 114L, 115L, 116L, 117L, 
118L, 119L, 120L, 121L, 122L, 123L, 124L, 125L, 126L, 149L, 150L, 
151L, 152L, 153L, 154L, 155L, 156L, 157L, 158L, 159L, 160L, 161L, 
162L, 163L, 164L, 165L, 166L, 167L, 168L, 191L, 192L, 193L, 194L, 
195L, 196L, 197L, 198L, 199L, 200L, 201L, 202L, 203L, 204L, 205L, 
206L, 207L, 208L, 209L, 210L, 233L, 234L, 235L, 236L, 237L, 238L, 
239L, 240L, 241L, 242L, 243L, 244L, 245L, 246L, 247L, 248L, 249L, 
250L, 251L, 252L, 275L, 276L, 277L, 278L, 279L, 280L, 281L, 282L, 
283L, 284L, 285L, 286L, 287L, 288L, 289L, 290L, 291L, 292L, 293L, 
294L, 317L, 318L, 319L, 320L, 321L, 322L, 323L, 324L, 325L, 326L, 
327L, 328L, 329L, 330L, 331L, 332L, 333L, 334L, 335L, 336L, 359L, 
360L, 361L, 362L, 363L, 364L, 365L, 366L, 367L, 368L, 369L, 370L, 
371L, 372L, 373L, 374L, 375L, 376L, 377L, 378L), class = "data.frame")

Thank you very much for your help. 

A:

Do it like here (in aes fill should be the column NAME not the VECTOR):
plot <- ggplot(mockdata, aes(variable, Measurement, fill = plotval)) + 
    geom_tile(colour = "dark red")  + 
    facet_grid(category~type, scales='free', space='free') + 
    scale_fill_gradient2(limits=c(-20, 20),high = "firebrick3", low = "dodgerblue4") + 
    theme_minimal() + 
    theme(axis.text.x=element_text(size=28, angle=90), 
          axis.text.y=element_text(size=28, face = "italic"),
          strip.text.x=element_blank(),
          strip.text.y=element_text(size=20, angle=0)) + 
    labs(title="", x="", y="", fill="")

