Goo, now that you’ve described it a bit more…
one thought is how sure are you of your platinum alloy? I see your
supplier is trusted but could a mistake have happened at their end?
Have you had a chat with him/her?
Because the rhodium is applying but not ‘sticking’, that suggests to
me some basic incompatibility of the metals. If it were just a matter
of cleanliness the rhodium wouldn’t apply or would be spotty. By
chance if you happen to still have a sizing piece or maybe cut off
prongs you (or your caster) might be able to run some tests on those.
I’d also look very carefully at the electrocleaner. I’ve found once
its been overheated I get crappy results, although peeling has never
been one of them.
But the job is promised (I assume) and needs to be delivered. Your
choices are continue to unravel a mystery(who knows how long that may
take), start again($$$), or job out to a laser welder for the repair
with no rhodium.
I’d be really interested in how this finally washes out.