Unwanted shortcuts through stock??

[LN-JET]

Hello, I have Rhinocam 2, and have sometimes the problem that it makes transfer moves through stock. Depending how deep, it breaks tools or looses steps. It is usually in horisontal roughing it happens. Typical setting is 0.5mm material left, and clearance set to 1mm skim height. I try to avoid clearance plane on 3d operations, as it takes so much time.
I have tried the stock and part offset settings, but I do not understand what they do. I miss a complete list of commands, and what they do.

The unwanted toolpaths can always be seen in simulation, but they are not easy to spot.

Lars