wow, I really have been away a while. Hope you got this sorted, but if not:
I'd try some 3 in 1 oil, go easy and keep it only on the threads as much as you can.
If the bronze is like the hardtail fly, then there's small threaded bushings inserted into the wood that the grub screws go into.
Then just do a few turns at a time, loosen, go a little further and continue until you get it where you want it.
I'll ping you later!