HenryLoenwind/EnderIOAddons#14

I think it's this:

protected void drawScaledFaceDoubleXY(
        float minU = 0;
        float maxU = icon.getIconWidth();
        float minV = 0;
        float maxV = icon.getIconHeight();
...
   icon.getInterpolatedU(u), icon.getInterpolatedV(v)

getInterpolatedU() takes a value between 0 and 16, where getIconWidth() gives the size of the icon in pixels. Vanilla icons are 16x16 pixels, so it sometimes works.

You're right, oversight on my part, will fix.

InfinityRaider@a7d67b5

Tagged wrong issue in the commit, damn you tiredness.