I learned this a long time ago the hard way.
That’s exactly what happens to sintered BRONZE when you slip it very much.
IIRC one of the very first trade names for sintered bronze was Vel-V-touch or similar.
You can not slip that materiel very much or it does exactly what you are seeing. It can’t take the heat.
That’s why there is sintered IRON discs. They will take the intense heat caused by the application of the clutch. Or if you slip it.
There is a HUGE difference between applying the clutch and slipping it and they ain’t the same.
I don’t know what to tell you about what to do that won’t cause massive butthurt and much wailing and gnashing of teeth but even Ray Charles can see you’ve got issues.
If you go back to what you are doing expect the exact same results.