But the journal is passing through on-disk controller, too. If the drive is
mishandling its on-drive cache, then an FS corruption is still possible. Even
if journal writes are "direct", the drive could be ignoring that (i.e. caches
it nevertheless) without flushing it prior to power-off, corrupting the journal
If the FS survives through reboots, but falters when the laptop is power
cycled, then a cache flush issue is still probable.
Another test method might be hibernation. If resume from hibernation works,
then that rules out on-disk caching problem.
(Somehow your message went to spam)
I'll try hibernation test. Good idea. This behaviour has to have something to do with cache. I don't see how this could happen otherwise.