Your guzzler is a diaphragm pump and very sensitive to ANY leaks. Can you check the vac closer to the pump and work your way up from there? You shouldn’t have sap holding in the mainlines unless it is sags with frozen spots? Are you sure the pump is hooked up correctly?
305 taps on 2 Shurflo's, 31 taps on 3/16" and 229 taps on gravity. 565 in all
Mountain Maple S3 controller for 145 of the vacuum taps
2x6 Darveau Mystique Oil Fired Evaporator w/ Smoky Lake Simplicity Auto Draw
Wesfab 7” filter press