No priority on the Geothermal Heat Pump

I'm at the part where you have to deliver 1.2t of steel to the geothermal heat pump.  I'm not able to get it done because the pump seems fixed at priority 5, and I'm not able to change that.  Thanks to the new relocate function, I was even able to put the needed steel at the base of the pump, and somehow, some was delivered (about 45-50 cycles ago now), but nobody will actually deliver the rest.  I've tried making tidy/deliver tasks the highest priority for several dupes, but the task never gets lower than 14th.  I've tried turning on proximity and keeping them in the area, but that didn't work either.

Suggestions would be appreciated.