https://bugs.freedesktop.org/show_bug.cgi?id=107978
--- Comment #50 from Shmerl shtetldik@gmail.com --- I think I know what happened. When I was rebooting, I still had the older kernel running (without the fix), to actually test the new one, so probably the bug still kicked in after reboot.
I now rebooted a few more times already from the patched kernel, and I don't see the issue anymore. It also doesn't happen with boot from complete off state.
Thanks!