With FSXWX running, I can cause FSX SE to crash by making a change to time/date or by saving the game twice. It only crashes the second time one of these actions are done from the toolbar.
I don't have FSX Steam, so I can only speculate: maybe it has something to do with simconnect.
Apparently, other addons also have this problem and various answers/reports suggest that you have to install the legacy simconnect interface.
Thus, go to "C:\Program Files (x86)\Steam\steamapps\common\FSX\SDK\Core Utilities Kit\SimConnect SDK\LegacyInterfaces" and install all "SimConnect.msi" in each subfolder.
At least, maybe worth a try...
Regards
And in case any other FSX Steam user reads this: please tell if you have the same problem. Thx.
Regards
I found deleting the wxstationlist.bin in your %appdata%\Microsoft\FSX folder also helps with random crashes. This file will be automatically rebuilt when FSX is started the next time.