Pitcher pump on gunk

Hi, thank you for the great game.

I've made a small 3x1 pit to store gunk and placed a pitcher pump over it (for manual gear balm production).

However, when dupes try to pump out the gunk, they repeat the animation and nothing happens.

I've attached 2 videos (with different dupes).

It happens when the amount of gunk is near a specific value (12.9kg and 12.5kg in the video)

If it is not intended, I hope this bug would be resolved.

Thank you.