@Blu3wolf:
It appears to have indeed been some mess with my DX setup.
The issue was with the shifted layer. Specifically, that I was pressing the pinky EXP FOV button on the stick. This button is the shift button, although my keyfile deliberately does not contain a shifted layer. In 4.32 I had disabled the shifted layer - however in 4.33 it was enabled by default.
Setting the shifted offset from 256 to 0 disabled the shifted layer, and I can confirm the EXP FOV button works as intended now. It seems that without any shifted layer present, pressing the shift key interrupted all the other subsequent keypresses from getting through.
Blu3wolf, can you explain how to " disable the shifted layer " ?