Many LPX plugins suddenly fail verification - suggestions?

After a long period of relative stability, Logic (now v10.2.2, in Mavericks) is now rejecting a LOT of plugins for me that it had no problem with in v10.1: Kontakt, Reaktor the v2 Applied Acoustics instruments, everything from Fabfilter, Melda Prod, kilohearts, Waves, Toneboosters, most of the DMG plugins.

All of these appear in the Plugin Manager as "crashed validation". What's so odd to me is that when selected and rescanned, pretty much every one of them is successfully validated, but then their status doesn't change in the Compatibility column, and they're still not available for use - the successful rescanning process has no effect at all. As a result I get the "scanning new plugins" with every boot of Logic, with dozens of "new" plugins every time.

So far, I have

• trashed the com.apple.logic.pro and com.apple.logic10 files (Preferences, user library)

• trashed the com.apple.audio.DeviceSettings and com.apple.audio.SystemSettings files (Preferences, main library)

• trashed the AudioUnitCache file (Caches, user library)

• trashed the three cache files in the com.apple.logic10 folder (Caches, user library)

• reinstalled the app from the DMG file

• even reinstalled many of the plugins in question and batchmodded them (just to say I did)

• reinstalled earlier versions (10.2.1, 10.2, 10.1)

Not sure how else to address this. I'm not seeing similar complaints online, though I haven't scanned the universe yet. It feels like there's a permissions issue somewhere, where the data that would acknowledge the plugins' changed status can't be written, but I have no idea where that would be.

I'm using LPX v10.2.2 in OSX v10.9.5 on a 3.5 Ghz iMac 16Gb/3Gb fusion drive. I intend to eventually upgrade the OS to El Cap or Sierra (and Logic to v10.3.1), but at the moment I don't have time to troubleshoot the inevitable compatibility mess that would arise with such a loaded system, and some of my most important working plugins are no longer available, so an OS upgrade will kill them off.

BTW, none of the failing plugins is out of date - according to the various developers, I'm up to date, except with the Waves bundle, which needs a newer OS to be current. I'm using the same plugins in my MacBook Pro (2015) with LPX 10.3.1 in El Capitan without any problems - which is what makes me suspect a corrupted pref or cache file somewhere.