PT unexpectedly quits - Session corrupted after relaunch

[Mischdepp]

I have recently updated a clients HD Native system to Pro Tools 2018.3
I did a clean install of OS X 10.12.6 on a new SSD and then installed the drivers, Pro tools, plug-ins etc. (previous system was 10.9.5 Mavericks and PT 12.4).
Computer is a Mac Pro 5.1 with 24GB of RAM.

My Problem is that when I open sessions they load fine I can press play and stop one or two times but then the spinball appears and I have to force quit PT.
After restarting the Mac and rebooting Pro Tools the session does not load at all but brings the spinball back immediately. The only way around is creating a new session and importing all the tracks from the corrupt one.
The new session will then work fine for some hours but then the spinball reappears out of the blue and I have to repeat the procedure (new session, import tracks from corrupted session).
This is annoying and I also end up with new folders for each new session and audio located in several audio file folders.

I first suspected auto save to be the cause of my trouble but PT continues to quit after disabling auto save.
Video engine is off because I use VideoSlave.
No VI's just a couple of audio and aux tracks for voiceover recording of tv documentaries.

No WiFi and the problem occurs on internal and external drives.
S3 connected via Eucon (eucontrol 18.3.0.244 and firmware 1.2.0.131

Any ideas for a cure

[ibbod0]

if you hold shift while opening a session, it makes all plugins inactive. can you open the corrupt sessions this way? if so, it may be an issue with a certain plugin or combinations of plugins going by my past experience.

[Mischdepp]

Thanks for the quick reply.
I think I found the problem - it seems to be the VisLM plug in from Nugen Audio.
When I close the plug in window everything works fine.
Just contacted Nugen support.

[climber]

So many of these kinds of issues are plugin related.

Just sayin....