Tumbler Problem

[lesley]

I've had this problem for a couple of months. The tumbler doesn't work when laid flat, only when propped up on one side - see piccies.
The motor's working fine and both the spindles/shafts move freely. It's always tricky getting the lid off so I think the barrel might be slightly misshapen......although I can't see anything.

I'll get a replacement barrel in the new year but I wondered if anyone else had experienced this and if it is a common problem?