If ever any of my (older) keyboards misbehave I just lift the lid off and remove then replace all ribbon cables!

I don't have a 540. I do have a 630 but I don't know how much is relevant, but I'll plough on nevertheless!

You may be able to stop the DAW setup locking by making sure that the PSR only transmits note / pitchpend (/ Program Change?) information (and maybe sequence controls like start and stop)(You might be able to do this by editing the midi setup of the psr). Any other midi data is liable to be specific to the PSR and so might be causing the DAW to get confused.

Alternatively (or maybe as well) could you configure the DAW to accept only key, wheel and program change events?

Regrettably I don't think the PSR will let you remap controls at all. You can't do this at the DAW end can you?