Some of us still here😁
FSX has always been unstable and when I was using it I had endless issues with crashes.
There are a some good tips on this site for dealing with wobbly fsx but by now they probably buried a bit now. Try searching the site using terms like FSX Crash.
Having said the above I don't have any experience with the Steam version so I can't be sure that any wise words found will work with the steam version.
My personal experience with FSX weren't good with respect to stability, so I upgraded to P3D. This helped a lot but still not so good in some circumstances. Eventually I gave X-Plane 11 a try as a parallel install and I have found it to be very stable In deed. I have now given up on FSX and P3D and stick to X-Plane 11.