Had a good one the other night. We are using a customized OSP200 4th axis post. When X4 converted it it changed the the flag that allowed the post to optimize moves by moving X;Y and Z simultaneously. We had it turned to Z then X and Y, break moves< in X3. Since we work with a lot of surfacing tool paths we have it set that way so it won't shortcut through a part. Verify looked real good but after the coolant cleared we noticed that the part had been nibbled away at in an odd way on a corner. The guy that programmed it was studying it and looking at his tool paths when he noticed the shape closely matched the feed lines for a small radius bullnose that did all the surface finishing. He found the problem in the post. Got to love CIMCO file compare It showed a couple of other flags that where different in our backed up post from the converted version. Anyhow I thought I'd post it for what it is worth.