This solution comes with an anecdote:
One Saturday afternoon in Nov 2013, I took a train from Antwerp to Neerpelt. (no, that is not yet the solution).
In Lier the conductor made the following announcement:
“Ladies and Gentlemen, since the toilets in this train are not working and we have a group of children on board, we’ll make a 10min pee stop at this station.”
The picture I made while waiting.