I doubt it's the Bishop to blame I use one myself, if it was or if it was your technique, you'd be seeing the problem more often. You say it's just a few times? The answer may be very simple,some people,thankfully not many, are bad healers. No matter what you do,they scab up bad. I once had a guy who was having a lot of tribal and we had this issue,no matter what we tried he scabbed up bad. At the time he was living with a nurse and she fetched home some medical grade burn dressings, it worked, finally he was healing up normally.
There is one mystery here, you say you run your Bishop at 9.5 and it gets hot? I run mine between 10-12 and it doesn't even seem to get warm-get in touch with Franco.