What went wrong? King 3B slide seems ruined :-(

[berntd]

Update:

I have my trombone back. The slide is still as terrible. The sandpaper like sound puts tears in one's eyes.
It does not even want to slide easily by itself when the trombone is held sideways with the slide tilting clockwise as in playing position. It is devastating all over again.

Does anyone have a recommendation of another technician in Sydney or even elsewhere who can sort this out?
There has to be someone...

Best regards
Bernt