Kind of says it all in the subject.
I bought some more BB last week or so, and my masking which worked well (transferrite) on the previous batch was just peeling up like crazy. I looked really closely and there were tool marks on the surface, shallow grooves running the whole length of the wood.
I gave it a quick sanding with ~400 grit sandpaper, wiped all the dust off, and I was back in business.
Maybe it’ll help someone else too, so here I am