Created an account to say that this fixed my issue. Have been having problems on and off when in the menu (before going to world map) and also in game where the FPS would drop from 25 down to 7 and sometimes slightly go up to 12. Looked at the FPS counter and it was locked on main thread & manipulators.
Turned off Online Functionality as you suggested and bang - back up to 25. Interestingly I also turned off each individual option but it still was bad so there’s obviously something that Online Functionality is doing that isn’t one of the things listed…