OKAY, FIGURED IT OUT. The new liquid loader port on the spacefarer module jams up if you have a gas pipe connected to the gas loader port that backs up. So there's some code in there that says, "okay, port's full" that's stopping ALL ports on a given spacefarer module despite other ports being available for use. Also, the gas port getting backed up completely stops all motion of gasses in the pipe. You can't have gas pass through the inlet to try to keep it moving in an attempt to bypass the blockage (as a workaround). Once that inlet's full everything's backed up until you can free it.
Here's some sample footage:
Create a spacefarer module with a liquid reservoir inside, then hook it up to the exterior ports and pump some water into it. Then connect a gas pump to the same module and pump gas in until the module is full up. Once the gas pipe is blocked the water will stop flowing until you find some way to clear it (the gas trapped between the inside/outside needs to be cleared before the water flow can start again).