Hmm, Just finding this again as it has fallen back to page 2 behind a pile of other topics.
Are we still saying the oil pressure did this?
The fracture looks like it matched the O.D. of the filter.
Could have a previous owner attempted to install a wrong/too tall filter and attempted to squash the cover on? It looks like a cookie cutter punched it out.
Find it hard to believe that the filter media didn't puncture. Damifino.
I guess replace the filter, spring, o-ring and cover. Then see if it repeats. ??? I hate to say that when the cause is still unknown, but at least there would be confirmation of a real prob.
Most oiling systems have a bypass of some kind, perhaps somethings is stuck?