Problem
The blade comes off the band wheels.
It is impossible to properly place the blade on the blade guides (blade too far forward or backward).

Cause
The band wheels are not properly adjusted.

Solution
Adjust both band wheels (see Adjusting the band wheel position (p. 91) in your manual).

Cause
The drive belt or band wheel belt is worn.

Solution
Replace the drive belt or the band wheel belt.

Cause
There is play in one of the band wheels.

Solution
Tighten and lubricate the band wheel bearing (see Tightening and lubricating the band wheel bearings (p. 92)).