I retried this functionality in vice 3.6.0, and there the functions keys works as intended! I can only draw the conclusion there are issues with either the backbit-cartridge or the c128.
Viewing post in Fix for NTSC when you die. comments
I've tested the game with Backbit on 2 additional c64:s with different revisions of motherboards, and there are no problems with these. Which leaves me with the conclusion that the c128 is the only platform that displays this behaviour. However, on the c128 it only occurs after playing for a while, tested death after level 3 and dying. Immediately pressing F7 after game have started cause no issues. The tests on the c64:s was similar to the tests on the c128.
Thanks for testing so much! We don't have an actual c128 to test this with or a Backbit, so it might be a hard one to fix. We have taken note of the problem and will see if anyone else reports the same problem.
We are not sure if there will be a fix for this in the near future. Sorry for the inconvenience. 🙂