Power booster issue

[69hugger]

I have a 9" dual diaphragm booster & stock GM master cylinder powering my Baer 6S 14" front & Baer 12" rears. The brakes have been working perfectly until the last week or so.
It has started losing power assist randomly.
The engine has good vacuum. I have checked the check valve that snaps into the booster & it works fine. I'm fairly certain there are no vacuum leaks, and wouldn't think a vacuum leak would result in a random failure.
My question is whether a failed/ failing booster can do so randomly? Could 1 of the 2 diaphragms be bad?
I am happy to replace the booster, but hate to do so & find I have the same issue. It is the end of the season up here & it will be 5 or 6 months before I will know.
Anyone ever experienced something like this?

Thanks for any thoughts.


Bill