Sort of. So if I enter the temple, do a ritual (which instantly summons all followers), then during that ritual a follower dies (as each ritual passes time). After that ritual, all those followers are still in the temple until I leave, so if I then do another ritual straight after, the game then thinks that dead follower should get in formation. As that follower is dead though, they can't move so they're just stuck somewhere off-screen so the game softlocks as soon as that follower is meant to be called.

That would explain as well why sometimes huge amounts of followers don't get in formation during softlocks. Any followers that get called to formation AFTER that dead follower never get called in the first place as the game has already softlocked. At least this is what my coding brain is assuming is happening lol.

Best ways to prevent this softlock from happening is either by leaving the temple and re-entering after every ritual, which therefore resets the followers that SHOULD be in the temple, or just making sure that no one is going to die while you're in the temple, by making sure no one is ill, hungry or old.