What version of Realism are you using (and SPT Aki version) and is this a recently issue that has popped up with an update or change of game version or is this an ongoing issue that you are having?
Ultimately this is VERY unlikely to be directly related to Realism or any of the changes that it makes, it may just be that Realism is causing more of a performance impact on your system. Generally instability such that you are describing may be due to overclocking, is your ram, cpu or gpu overclocked? If I had to guess it would likely be related to ram.
I'm using the newest version of Realism as of yesterday, 3.5.5 with the hotfix. I waited to upgrade SPT to 3.5.5 until Realism released with 3.5.5. My SPT is 3.5.5, but the same issue was occurring in 3.5.3 AKI with 3.5.3 Realism mod. My profile is carried forward from 3.5.3.
It is not an issue I have had with SPT in the past, I've only recently began using Realism mod though. I would say at this point that it is an ongoing issue from 3.5.3 on to 3.5.5. No data before that as I didn't run Realism on a version prior to 3.5.3. I also skipped 3.5.4 as Realism wasn't updated for 3.5.4.
I also thought it would be a RAM issue at first, but I have 32GB of RAM and when monitoring performance via Task Manager I don't max CPU, RAM, or GPU during the crash. None of my hardware is overclocked either.
The crash also happens both in raid or in the menu. And none of my other games share the same problem. A fresh 3.5.5 install with my 3.5.3 profile and no mods experienced no crashes at all in a 3.5 hour session. Most crashes occur around 30-45 minutes of play.
I don't want it to be isolated to this mod, as I love using it. And I also sure as heck don't want to play SPT without it. I also thought it was highly unlikely to be this mod until testing the game with with other mods removed kept giving me the same crashes. I'm currently limited to high speed Factory runs. Some of those even crash before I can extract.