We've made a recent upgrade from Moodle 3.4 to Moodle 3.7 and found that all H5P content of type "Interactive Video" stopped working. When attempting to view or edit any H5P interactive video on our Moodle site, we simply get a timeout resulting in bad session locks.
I'll list all the relevant specs and changes I can think of:
New Moodle version: 3.7.4
Change of $CFG->cachedir and $CFG->localcachedir
Content Type library updated from 1.21.2 to 1.21.8
Servers (both production and test) are running memcached for sessions
H5P version is 1.20.2 on both servers
Directory permissions are identical on both servers (777 for moodledata and separate cache dirs)
I've tried to replicate the issue on our test system and was successfull in doing so by simply moving said cache directories to their default location (in moodledata) and back (to their custom directory). That was enough.
Strangely enough, on our test system, I have been able to remedy the situation by simply deleting "cache", "localcache", "sessions", "temp" and "trashdir" (in both paths where applicable). On production, this doesn't seem enough. Only two differences between the systems:
1) Production has internet access and thus
2) Production has more current plugin and content type versions (see 1.21.2 vs. 1.21.8 above)
I'm at an absolute loss. PHP Debugging on max level is not helpful:
"session_start(): Unable to clear session lock record"
I'm hesitant to start playing around with session handler, etc.
My best guess is some interaction between H5P and the moodle cache. But not sure, how exactly... and even less what I could do about it.