Help with torch height position during cut

[lazybear]

Ok, I've been cutting stuff for a couple of months now and all of a sudden my torch is doing something interesting. The torch pierces just fine, starts to cut fine and then, in the middle of the cut, the torch head raises itself up while the torch is still cutting. It looks like it is going up a hill but the piece is obviously flat.
I didn't change any settings, and right before this happened, we cut three pieces perfectly fine.
We're using a Samson 510, hypertherm 65, fine cut consumables. Cutting 14 gauge steel. Nothing fancy or intricate, just a basic design.

Any ideas??

Thanks in advance!
Stacey

[lazybear]

Also, we do have advanced height control. Thanks.

[mike 1948]

Is your ground clamp on the material?

[marcnaz]

If the error repeats it sounds like a THC issue. If nothing changed in your software settings or your post processor and you have made sure all your connections are good and you have new consumables in the cutter then the THC is the likely culprit. I'm assuming the air pressure is correct and maintained throughout the cut? I suppose it could be interference or something causing a voltage change to the THC (dirty table slats or going over a thick support bar or something) but not as likely as a THC issue.