If you absolutely must go thru the Channel, use the "." key to shadow you sub. But you must have the outside camera turned on in "Realism" settings. That way you can see ahead of you and avoid mines and subnets. Not as real as true life, but it works to get you where you want to go.
But as said... "Stay out of the Channel". You're only asking for trouble in there, not only from mines but from the Enemy's warships too.
Any sub commander east of the Channel will go north thru the North Sea to go around to get into the Atlantic, if they absolutely must.
Besides, it's not a "mine" bug.