Why Are My Sims Catching Fire From The Toilet?

I used to get that a few months ago, identified it almost right away and had to delete toilets and upgrade them manually.

This composing thing is really a silly thing to have in the game when it is guaranteed to catch fire after a few uses. I also have no idea why the developers thought it would be a good idea to add the composter to the instant upgrade when it should of been left to the base game upgrades and any upgrades from eco should be left open to the player.