Its a tough navigation problem for the AI (in between islands of the Phillipines), but running in SE in 3.6.3 all groups managed well, while in 3.9.3 two problems are apparent
1. 3 groups never leave their initial position (they are on ASuW patrol with many ref points)
2. groups replot their position and follwo strange paths sometimes even going backwards.
I believe this is a serious issue which would warrant some testing and searching.
The screenshot is of a new scen which suffers from it. I'll publish it shortly as there is little I can do about it.
Freek