Just disabling all 4 of them should work. I'll need to poke the code which tries to import the bb-code if they are missing but preserve existing it might not be working at keeping the 'active' flag respected.
Do you really mean "disable", not enable? They were automatically disabled after the update and this is where the issue started. Enabling seens to have solved it. Kind of. I enabled all four yesterday and just checked again. Two were disabled again, two still enabled.
So possibly a maintenance job that does something weird. I've now enabled all of them again.
Checked the logs, I see the event of me enabling h3 and h4 yesterday and h1 and h2 the day before yesterday. There is however no log entry for enabling h3 and h4 despite I definitively did that, so it seems these were not recognized, whyever. Maybe I rushed to another page of the ACP too fast after switching them on.
Did not find anything that had turned them off since the log entry for the upgrade of the BB Code add on.
They are still set to on, so possibly no maintenance job and the switching off still seems to be suspiciously connected to the add on update and done by the installer.