So I've basically been playing coop since it was unlocked and never noticed this issue until now. I decided to try out some of the single player only-missions/side quests and I found that after doing some of the Outpost Master quests or Racing quests, after finishing, the game would not load properly. The Options menu where you choose all the game settings worked fine and opening up the Map menus worked fine, I could even choose to Fast Travel to other locations but the game would still load the same way. Not sure why. Please see screens below. If you need further info, just let me know and I'll be happy to oblige.
Spoiler: Show