Since SU10 beta, some users are experiencing a weird behaviour around defaulte boats/ships : best description can be "Grey rotating lines"
The issue looks like to be related to the wake effects (assumption based in the location of the point where the weird lines are generated). I'm not experiencing this issue, but already seen those line when playing with effects editor, those line where generated when the wrong bitmap was used for that effect.
Some samples of the issue collected on official forums and my discord
Hope you find some repro steps for those!