Just wanna flag one thing here, PSP has been an issue here too with both Sierra and the following update to High Sierra.
We had bought a bunch of them and unknowkngly installed them and forgot a out them. I noticed this issue after a few weird things last year on one of our Trashcans here with 12cores and 64GB ram all SSD’s which should be awesome but had some bad behavior.
I trashed all the PSP plugins and vσila! No more strangeness so follow Darryls steps and advice with moving them out of the AAX folder as they cause havoc by just beeing installed, not just when instantiatedz
And furthermore as Darryl pointed out turn off any cloud stuff as it seem like many have problems with dropped sessions and hanging of sessions etc when connected and using Cloud Collab unfortunately. Use the save function for the local drives only so you are 100% sure that internet is not interfering with your sessions.
NY1 want some PSP plugins
we will never install them again. Not that great either so no loss ... except the monetary outlay but I value my time more !