I've made also an additional test ( same single mission ). Once spawned ordered ahead flank then ordered a constant 25° turn to port and kept it for 10+ mins. The flag remains stuck/waves always in the same direction ( Like in the image I've posted above )
CROSS LINK: https://www.subsim.com/radioroom/sho...&postcount=818
* Another odd behaviour of that single mission is that the crew never close the conning tower hatch if you order periscope depth.You have to close it manually otherwise you can make a bit of scuba diving 