iOS 14.4.2 e iPhone 6s
i can tell you it's a problem for tomtom, because garmin has no problems! personally tested! yet they too have their own GARMIN DRIVE app which performs the same functions as MYDRIVE, never a disconnect!
And yet -- if you were running iOS12, you would have no problem.
Something changed in the iOS BT stacks between 12 and 13. Not saying TT shouldn't have sorted this out, but they weren't the only ones that got caught by this. Good that Garmin got it figured out.