Originally Posted by
himespau
I took the bike to the local shop and they've tried a couple more penetrating solvents, as well as apparently heating the BB shell and cooling it down. It doesn't move.
I am no kind of chemist but shouldn't the mechanic be attempting to loosen the cup while it's still hot? The heat will temporarily melt the threadlocker, but if you let it cool down again, I imagine the threadlocker will solidify again.