not seen anything like this. Sounds like something in one of the mods making up Onealex interacting with SH3 AI.
In GWX there is a German minefield near Wilhelmshaven, near the entrance to the Jade bight. These mines are marked on the minefield maps available as pull downs on the map screen. There are also some unmarked British mines nearby to the east of Heligoland which I have encountered a couple of times
. Normally GWX mines are spread thinly and moored to float well below sea level, so they not visible from the surface; I would guess this was a bodge to avoid interactions with the AI. Did someone "fix" this in another mod?