I just checked my JLC GG1, the good news for me is it seems perfect, I don't see any evidence of rot starting.
Given the mention of the P5a, I thought I should check that one as well, but I don't see anything happening there either.
My only recent encounter of my own stuff was a bunch of K-Line passenger car trucks, they were crumbling as I watched! I also had some freight cars with the wheelsets rotting away, that was a fairly easy fix.