I'm curious about this because I've never had issues, but such a claim is very likely going to scare people off using that mod.
Topic on Talk:Syndicate (2012)
I'm encountering an inability to have the game save or keep video settings with the FOV mod enabled. Not sure how to fix it, I've tried changing compatibility mode and other common solutions but nothing seems to work.
Correction: My progress, video settings, and key bindings are saved but not accessible with the 90FOV .dll. Switching to the original .dll allows access to the save file and restores original video settings and bindings.
Apologies for the comment chain. I've found that running the game as Admin allows me to access my custom video settings, bindings, and saves while keeping the modded 90FOV .dll
Note that checking the box to run the .exe as admin doesn't seem to work, nor does checking the box and using Origin to launch the game. Right clicking and running it as admin every time seems to be the only way I can get the game to start in that mode. I'll experiment a bit more and might add my findings to the mod's section on the page.