GSF1200 Clutch Slipping: The Thousand Yen

This is a GSF1200 from Oka Village, part of the Yaruze chain.
We’re already on the fourth time removing the clutch cover…
Well, I’ve been super cheap about this,
“Just remove this and it’s fine”
“Just replace this and it’s fine"
"Add this and it’s fine”
In the end, the friction plates hardened, so we weren’t getting any results
“Stop being cheap and replace all the plates,” we concluded.
 

 
I hope it’s just my imagination, but the transmission feels loose—it’s a bit sketchy.
Thanks for your hard work!