@wowgetoffyourcellphone sorry for the delayed answer. Given that @elexis is not done with the GUI rewrite I'd suggest you remove the gui/session/ folder until everything has settled down.
From : http://irclogs.wildfiregames.com/2019-10/2019-10-21-QuakeNet-%230ad-dev.log
17:18 < Stan`3> Also I believe one of your commits broke delenda est
17:18 < Stan`3> https://wildfiregames.com/forum/index.php?/topic/21573-ugh-okay-help/page/5/#comments
17:18 < elexis> "one"
17:18 < elexis> he copied the files
17:18 < elexis> so each time I modify a file that he copies it "breaks" it
17:20 < Stan`3> Sure.
17:22 < elexis> I looked into making this civ thing more compatible, but that also requires rewriting everything again
Sorry for the inconvenience. Also for future reference, *.diff files are not used by the game so you do not need them