Gas reservoir will not empty if input pipe is not connected

I confirm this bug happenned to me. It not reproduced 100% of the time.

I tried deconstructing and rebuilding the pipe between the 2 reservoirs, and the output of the first reservoir wouldn't send any content.

Strangely, the flow began again when I made a build pipe errand on the input of the first reservoir (when I put the errand, not when it was build)

 

I didn't screenshot before the workaround, but it was this very setup, unless there was no gas flowing

Happens with liquid reservoir as well.