I turned the flow sensor off and ran the print overnight, sure enough I could see in the morning a problem with the PVA. It's still running now, and has another 4 hours to go. The PVA is stringing all over the place, and I'm sure its because of humidity. The reel has been sitting open for a week mounted to the back of the printer. I think the print will be OK, but still, real extra care has to be taken with the PVA to prevent this. I didn't realize it would be so sensitive to humidity.
Should standard procedure be to unmount the reel every day and store in a bag with the moisture absorbant?