Hi,
aTc just mentioned on IRC some problems with kernel 5.9. I dug out my
old 5.9-rc1 tree that I was testing with and found this patch,
attached, that I don't think made it upstream and might be part of the
solution (I haven't tested it on newer 5.9, but it looks like it is
still relevant). Hopefully I will actually have some time to look into
things more this weekend.
Best
David