So, right now, there doesn't appear to be an alert system when cast segments of the colony are blocked or obstructed.
I once had a mask checkpoint block a portion of my asteroid and it became a pain.
My example is as follows:
To start, several duplicants die of suffocation. This is strange because they are moving to an area that isn't typically used, getting stuck, and then dying. Restart. Avoid them dying, but something is wrong.
For some reason, food production has snarled. Ok. Fertilizer is absent. Ok. Check the fertilizer plant. Online. Odd. Several dupes starve. Ok. Something is wrong.
Attempt to adjust priorities, errands, and yellow alert status. Ok. For some reason nobody comes. Odd. Cannot make sense of it. More dupes starve, fertilizer is not produced. Restart. Hmm.
Looked at the physical workflows and traffic. For some reason dupes will not pass through a certain area. Unsure why, as the buildings appear to be complete and in good order; no visible areas in what has now been interpreted as a 'unknown blockage area'.
Check each building, working backwards from the ones recently built. As it turned out, an oxygen mask checkpoint had blocked a critical artery, triggering chaos.
So, what I would like is some alert that blockages like this are happening. I don't know.