Issues with Koralia 2

[DiverDude]

So I removed 2 of my Koralia 2's this morning to clean them. One of them now makes a rattling sound -as though the impeller ceramic is hitting the sides of the motor housing.

I've disassembled and re-assembled, checked and re-checkd it about 6 times now and it keeps doing it. I thought that since the unit is pointed steeply down, there might be air trapped around the impeller (and there was) but removing that changed nothing.

I've got it unplugged for now since I'm not at home and I don't want to leave it unattended.

This unit is about 8 months old.

Thoughts ?