Relevanssi was updated today (June 21st).
https://www.relevanssi.com/release-notes/free-2-9-3/
Quote: “I’m sorry to report 2.9.2 was a buggy update. It had a very small bug — just an add_action() call to a non-existing function — with very large consequences. Fortunately nothing permanent, so a quick upgrade to 2.9.3 will fix this”.
I’m sometimes helping a family member with her WordPress site. Today her website showed much higher memory usage than normally. I noticed she had installed a new plugin (Relevanssi). I also noticed high cpu-usage (never seen that before). After the upgrade, things seem back to normal.
Unfortunately Mikko did not notify you in this thread (which probably got the ball rolling). And he doesn’t find it necessary to tell his users exactly what went wrong, and what the symptoms are. That stuff helps users to find the problem, so they can fix it. Even if it would make googling easier. Keeping your users updated is the first step towards keeping your users happy.