Functioning flushing toilet suddenly considered "out of order"

Are those 2 toilets all you have? For 17 dupes? Then the problem could be, any dupe, somewhere, is assigned to the toilet already, while the dupes in front of the thing cant use it, because its occupied. 

Yes. I have 2 toilets for 17 dupes. They are on shifted schedules with 4-5 dupes per schedule. As I mentioned, I've only had maybe one or two accidents in over 500 cycles. It's not that.

I also tried assigning the toilet specifically to one dupe, and they still won't use it. If there was no toilet, the message wouldn't have been "toilet out of order" but something about no toilet available. Also, doesn't explain why suddenly all my dupes couldn't use it.

Removing and rebuilding the toilets fixed the problem.

i´ve load your save, and besides your base is a total mess ^^, there seems to be nothing wrong. 

I've loaded it again, and the dupes still have "toilet out of order" exactly like in the picture above. So I'm very surprised you say you see nothing wrong.

Are you running any mods? I'm running none, unmodified game, no developer option, nothing.

Are you on Windows? Steam version?

 

(About the base, I designed the center area and kinda winged the rest... considering it's my second colony there was a lot I didn't yet experiment with. When I eventually make a third, it would be cleaner for sure )