Depends on the board and the details of your sim.

If you're talking about Minimum Defence Frequency -- it's just a heuristic; solvers don't follow MDF on every board. See this post of mine for an even more glaring discrepancy. Or, for a more theoretical example, where OOP folds their entire range on the flop, see this.

In general, overfolding happens on boards which are bad for BB's range. You overfold on earlier streets (where you have put in less money) to make your range stronger and make bluffcatching viable on later streets.

Think this is a bad example as it is checked 97% of the time and only bet 3% of the time. So prob to have a low dEV more time is consumed to balance the checking line then the betting line.

Pretty normal, check out EV and Equity for both players, they usually tell overall picture

Sorry, my bad, I completely forgot to mention that this is the solution of an entire database on 163 flops. Now you can definitely answer more consistently and anyway thanks for the previous answers.

Yes I would expect to see BB overfolding across many flops. This is because the initial discount to entering the pot allows them to enter with a weaker range. The larger the initial raise (and hence tighter the BB calling range) the less as BB you can do this.

The range simply is not strong enough to apply MDF. As mentioned MDF is a heuristic but imagine a game where X has 99 and Y has AA. In this situation X folds to all bets. GTO is not the same as MDF. The only place you see it always (90% sure, maybe there is a funky counterexample) apply is when someone had made a bet on this street and gets raised (2 player game). Their reaction needs to follow MDF.