Now I know why 904 was having issues

It did that because hardened shrinking rubber seals don't expand out and seal until they are warm and can move.
It causes what is called "Morning sickness" and is where the car won't move or is real sluggish till it warms up.
During that slipping it can hot spot the clutches and steels like that.
Either that or someone used burned plates from a previous "repair" and didn't replace the rubber seals.
(you said the clutches looked good) but to burn a steel surface like that they would be black or at least really dark.

The amount of burn on the steel can happen in seconds when a trans slips, and I'll also guarantee you that front band was slipping, and I don't think the damage to that drum was from that band.
(another reason to suspect a half assed repair was done where the friction parts were all that was replaced.)
If that band did that to the front drum it would be a mirror image of the drum with no friction material on it at all.

Next look at the second picture down (the inside bore) where the sealing rings rode.
It was moving forward and back enough to almost completely cover the slot where the fluid is supposed to flow to apply that drum, yet you say the endplay was ok.
(Did that happen before also, confirming the fact that most of this stuff happened at some point before and was just patched up?)

Sure is looking that way.