As a follow on to this, I have been in contact with a TF6000 user. From his logs, the problem seemed to be a serious memory problem. He pointed me in the direction of a German thread started by Gerti (who seems to be linked with Topfield now).

He states that as many API calls should be made in the Idle handler as possible, even responses to Remote keys. This is especially true for the TF6000 series. Now, handling all remote keys in the idle handler is a tricky business, not least because sometimes you want to pass the key press on, sometimes not. I did set up a simple event queue which I processed, but soon gave up when I realised it opened up a veritable can or worms.

However I did make a change to move all my init code out of TAP_Main, and performed it in the Idle handler instead. This seemed to make a big difference to the TF6000 user, who so far has had no problems (although it may just delay the problem).

Indeed, they seem to have forgotten that they support a TAP API in that firmware, which is slightly disturbing.

The init change was pretty easy though (I was doing all sorts of things in TAP_Main), and it definitley seems to prevent the occasional crash on startup of the TAP. Interestingly I used to get these myself sometimes, and adding or removing a few random lines of code always seemed to solve the problem.