In the picture here, the Soviet inf. can not leave Kiel by sea because the minefield just East is German. However Soviet supply gets in normally.
I believe there is one of two bugs. Either the minefield on the beach should be Soviet because the adjacent hex to the beach was captured by the Soviets.
Or, if the minefield should remain German (which would then beg the question of how to ever convert it?), then it should also stop enemy supply.
