Error: Cannot process input and RDP

[pidgtt]

The InputRDP demo only works on hardware, and the rectangle does not respond to input and only moves in the upper left direction.

The InputCPU demo works fine, showing the hardware is picking up input.
However when I add an RDP Buffer and DPC command to use the same code to move a rectangle, it no longer responds to input.

I've been compiling with armips, but I get the same results in both compilers.