Suggest testing the same branch with the alpha patch reverted just to
rule out any issue in the core code. If it reproduces suggest to
bisect Leon's branch.

I can try to revert just the patch containing the alpha-specific stuff and
see what happens and then, as  you say, maybe do a bisect from there.
First I'll just try the same kernel again a few times more just to make sure
that this is really reproducible.

/Magnus