HIPS filament shrinking - bowed in middle of print?

I'm printing some objects with HIPS and have this odd behavior of the layers in the middle of my print shrinking so that walls which are supposed to be vertical are bowed. It's worst at corners and the longer sides. Any clues how I might fix this? Is this a temperature issue or do I need to buttress the sides somehow? Bed adhesion is great. Thanks, Mel
Attachment 9665

What is your bed temp? Glas point for HIPS is betweene80 and 85. Anything over that and yes, your print will melt.

Thanks, Sebastian.

Bed temp is 110, extruder 235, same as I use for ABS. Printer is a Flashforge Creator Pro, FWIW. I'll lower the temp and give it another go.

Yeah try it at 80 or so. Maybe 85. Not sure what grade HIPS you have.

Thanks - I set the table to 83C and that seems to have done the trick. I'm using Gizmo Dorks filament, FWIW.

So it worked well with the bed at 82 and the extruder at... 80?