Please centralize all error reports here.

In Alternative Mod Uploader (AML), select Pistols Rebalanced, click the config tab, pick PistolsRebalancedDefault.ini, change bLog=false to bLog=true.

Save the change, then run the game with whatever incompatible content you have.

After going to the loadout menu, exit the game, open AML, click File, click "Open Log File", then click "XCOM 2 WOTC".

Search for "pistol" in the log, and copy any relevant entries. Paste them into your post in this thread.

If you don't feel like doing that, upload the log to Pastebin/GoogleDocs.OneDrive/etc and post the link here.