Metabo BAS317 Precision bandsaw

[GAG]

I have a Metabo BAS317 Precision band saw which I bought second hand a few months ago. The saw was in excellent condition and, initially, performed well.
Recently I used the saw to cut a load of oak and whilst I do not know if cutting the hard oak had any effect, I have had a problem with it since then. The problem is that the blade flies off the lower wheel after a few seconds of use. I have carried out the alignment and other checks in the manual but it appears to me that the bottom wheel may be slightly out of alignment left to right OR the two wheels are not running in the same vertical plane.
There is nothing in the manual about alignment of the bottom wheel so I have been in contact with Metabo and, whilst they have not really been very helpful, they have said that there is no alignment adjustment for the bottom wheel On some bandsaw I understand that it is poossible to remove a wheel and insert shims to correct the running planes but this appears to be impossible on the BAS317 since if you could fit a shim onto the shaft it would not be possible to refix the retaining circlip.
Does anyone have any suggestions for a DIY solution or do I need to take it to a Metabo centre?

 

[GAG]

In the end I did what I should have done at the start. - I took it into P.E.T. Hire Centre in Crewe
The guys there were great and established that the problem was a sheared bolt where the lower wheel shaft attaches to the body of the saw. On start-up this resulted in a small amount of movement of the lower wheel causing the blade to fly off which was one of those things that, working on the saw alone, you would not notice the slight movement of the shaft.
Well done lads - I would recommend P.E.T. Hire Centre to anyone if you are in the Cheshire area