[Wizzoboy]

The one thing that shouldn't happen is crashing when you do simple tasks such as closing a session. Trouble is there are many causes of crashes and finding the cause is not always easy.
There are plug-ins that will cause crashes, out of date drivers will, an inadequate graphics card, etc.
Now, I have been running 64 bit PT since version 11.0 on the same computer that now runs 2018.3. I have never experienced a crash in any of the versions I have used. Maybe it's because I use a workstation (which by the way is 12 years old) or keep everything up to date. I'm not alone as many people have stable systems.
There are, unfortunately, so many variables when using Windows that problems and conflicts can be hard to track down. The fact that you get a crash with simple tasks such as closing PT points to a problem elsewhere in your system.