I know this is two years old, but there were no replies, and in case someone else stumbles across this thread, RenderingConfig32.java, RenderingConfig64.java, Vec32.java, and Vec64.java all seem to define their structures incorrectly. Perhaps the way they are supposed to be defined changed.
To fix it, replace each occurrence of setIntAt(x, val) with setIntAt(x*4, val) (e.g. setIntAt(1, val) -> setIntAt(4, val))
Do the same thing with getIntAt(x), getFloatAt(x), setFloatAt(x, val), setFloatsAt(x, val), and getFloatsAt(x).
Hope this helps.