Dwell marks?

Hi guys.

NZ2000 T2Y2

Noticed this morning after setting up a repeat job, that there appear to be dwell marks evenly spaced on the face and OD of the part being m/c'd on spindle one.

They are timed to the rapid retract moves of the internal threading cycle that is happening on spindle two.

I have sync'd the turrets to avoid this, but am puzzled by the sudden appearance of this.

I have not seen it before. Not on the previous job, and certainly not on the last batch of these particular parts.

The machine is ~18 months old (but has been through a flood).

I initially thought some sort of mechanical or foundation issue, and the Boss reckons it's power supply.

Anyone seen and fixed this before, or suggest a place to start looking when I finish this run?

Thanks.