I copied this from here: https://steamdb.info/patchnotes/3788323/
So the hotfixes were for Phys-X issues.

I had no crash since release here, but started with hotfix2

I still get the odd crash, but not as often as I did before hotfix2.

I never had a single crash until after I unlocked the 2nd outpost, then it started to become quite common.

Changelog for Hotfix 1 (added 03 May 2019):

Survivors.

We heard you and we have been working hard to fix the issues you have with Fade to Silence, especially the crashes.

Hotfixes
We today released a Hotfix 1 that should solve the map- and sled-related crashes. Thanks to your crash logs and crash reports we were able to identify another possible crash cause. While this one will not be fixed in Hotfix 1, there is another hotfix in the works which will be released soon. For this fix, we will need your assistance since it’s not easy to replicate or even test the fix. We will publish another statement with more information on this soon.

Connection Issues
We also have a possible solution for the connection errors that some of you experience when they want to start a Co-op session. The reason for these issues is most likely resulting from router configurations and/or antivirus or firewall settings on the individual computers. The solution to the connection issues is simple. You need to open the following ports on your PC or router to enable communication between Host and Guest computers:

61110 to 61119
30000 to 30009

It may be the case that your co-op partners have to do the same. On information on how to open ports on your machine, please check with the manufacturer handbook of your router, antivirus or firewall. For further help on this matter you can also let our Customer Support know at support@quanticlab.com

Thanks for playing Fade to Silence.

Your team at Black Forest Games.


Changelog for Hotfix 2 (added 03 May 2019):

Survivors.

We today released Hotfix 2 that should resolve Phys-X-related crashes which is the the overwhelming majority of the recent crashes, thanks to our partners. With Hotfix 1 and Hotfix 2 now released, there should be a noticeable decrease in unexpected quits.

There is one more crash cause we identified and that we are currently working on. As soon as we have a solution for that, we will release another patch for Fade to Silence.

However, with the Hotfix we ran in to issues with coop connection. Please check if both the Steam and GOG clients running at the same time. There should only one platform running at the same time.

The last resort to solve this issue would be to restart the client and then verify/repair the game in 'manage installation' settings dropdown.

For more trouble shooting and more information, please contact our support at support@quanticlab.com.

Please continue to send bugs and crash reports to support@quanticlab.com whenever you encounter it. If you still experience crashes, please fill out the crash reporter and send it to us. The more information we have, the quicker we can fix the issues with Fade to Silence.

Thanks for playing Fade to Silence.

Your team at Black Forest Games.