It may be that we have fixed these bugs in 3.6 already. If the fixes are small, we usually also fix it in the latest non-beta (currently 3.5). However, if the fixes are large and/or otherwise have high risk, we only make them in the beta to avoid impacting non-beta users with potentially worse problems. We try to keep the non-beta versions as stable as possible.
There is a beta spine-unity runtime which likely has all the functionality you are using in 3.5, but I understand you may not be able to upgrade to the 3.6 betas. I don't want to push you towards the betas unless you are ready to encounter and report any potential editor or runtime problems (just the nature of the beta beast).
If you hit a crash, ideally you open Spine again, try to do what you were last doing, and if it crashes again post the log file, the steps you took to cause the crash, and your .spine file. I know this takes some time and effort and you have other things to do. The most I can say is that we are very serious about fixing such problems. They are our top priority. We can sign a non-disclosure agreement (NDA) to look at your project files. Often we only need the .spine file, not the images, so your employer may consider that OK without an NDA.
