Originally Posted by
Homebrew01
"cable tension " is not relevant in this case, since it's vintage non-indexing.
OP, you could try letting out the High limit screw a bit more, even though it will be a tiny bit too much when on the small ring, but riding small-small is not that common, and even still, it may be fine.
Its vey relevant. If the cable is too tight the RD wont rest firmly against the stop.
The OP's issues are classic symptoms of worn out jockey wheels, a tight cable or too short of a chain.