After cleaning & repainting by rear calipers I find that the cap covering the inside adjusting guts is stripped in the hex bore for the hex wrench.
I was able to get it loose with the old chisel technique but no way can I torque it back in after doing the inner adjustment. If that cap has to hold hydraulic brake pressure then i'm screwed as no way to torque it back in. If it's just a dust cap, i can use a vinyl plug
Comments from those who know ??

i have one of those plastic caps missing and nothing leaks, it covers the winder screw that jas it's own internal seal if i remember correctly.

The inboard cap doesn't hold hydraulic pressure. But it does need to be there. I suggest contacting PMB and getting a new metal cap like the factory one.

IIRC, Weltmeister also used to make (still makes?) plugs with an external hex, so you can use a regular socket instead of a hex key. The external hex has more surface area for the tool to fit on, so it is far less likely to strip.

A PO of my car made something similar by epoxying bolts onto the plugs. Without making them key into the hex in the plug. (Epoxy doesn't like to hold in shear all that well, so this qualifies as a Very Bad Idea ™ .)

--DD

Thanks all, our friends at AA are sending me a new one with the external hex.
Good times