You should try disabling dynamic plugin processing because it can cause problems. I would not have suggested it otherwise
AAE-9173 are not necessarily literally you are running out of total CPU, often it’s a very high speed glitch in the latency caused by something. Some plugins seem to have problems with dynamic plugin processing. I know developers that think it should never have been implemented. That may be one thing improved in 2019.5 (the first version I have left to run with dynamic plugin processing on).
What disk is the session on? In each case? “SSD” is not enough info, what make/model/spec and if in an external case etc how is it connected.
Sample rate? ... give some idea of session size/complexity?
Disk cache size?
Have you tried running the session off the internal boot SSD? If not you can try that. But importantly wherever the sessions are make sure the disk cache is set to a few GB at least and that when you start the session into memory watch the cache meter and make sure the session fully loads (meter goes green) with room to spare. Yep disk issues can trip up 9173 errors.
... but Plugins would be a first guess, so good you tested that. But to be clear the test you want to do is try moving all .aaxplugin files out of the plugin folder, trash prefs and restart Pro Tools, if you did not try that give it another go.