Dupes won't walk through airlocks and stall on a task

This seems to happen anytime a dupe has a task that requires them to sit within the airlock while they're doing it (so a task either right next to the air lock or within 2 tiles of the door).

However I've also observed that this behaviour doesn't happen consistently - some times a group of dupes comes in (for example to load a storage unit) and the first one or two get the stall behaviour but the rest behave normally (i.e., stay within the door and complete the task within the expected time frame).

It's also worth noting that when this happens, the progress bar underneath the task doesn't always appear - sometimes it seems the dupe is just doing nothing and staring into infinity 

Yup, like with mining on the other side of a door. No animation but the task completes regularly from the far side of the airlock with the door closed. I've only noticed this behavior with the DLC but it's been awhile since I played the original.