Heh heh spent 9$ on a bottle of Syl-Glyde. This is what I do if I can loosen the bleeder. If the bleeder is frozen , I trade it in for a reman.
On the 528e, I take the caliper off the carrier. Leaving the hose on, I carefully pop the puck out with brake pressure. The area of the cylinder where seal travels is above the "sump" where the water collects behind the bleeder. So the swept area is still OK. I take the puck out and wire wheel the rust off the top edge. This is the crud that sticks the caliper. If there is peeling in the chrome, I file the pit to smoothness. A light touch is all I ever have had to. I wire brush the bleeder screw until it gleams, making sure I can blow through it. Then I put it together using the Syl-Glyde as assembly lube. An 8 " C-clamp and a small hammer is all I use. The hardest part is the darn boot. I dont even bother with the rebuild kit anymore The seal on the puck has to be good, the rest is less critical. How I ramble.
To the OP, I would lightly pack some spark plug boot grease,silicone, into the boot where it hits the inside edge And fuhgeddabodit. When they get get worse, replace both calipers
This is with ATE parts 25 yrs old, YMMV. The generic procedure should apply to most calipers though.