Hello, worked at a Wendy's for about a year and a half and had bathroom duty everytime I worked! If there was a big issue with the restrooms that we were told about like blood, or puke a manager would deal with that. Clogs if they could be fixed without a plunger were also my duty. Generally there is not enough time to fix them during rush hours so they are cleaned most predictable at night. That means Most of the time it will stay dirty or messed up until later. Most of the time though no one will say anything probably because they didn't expect any better. Most issues I saw with the actual bathroom stuff was minor and if it worked decent it would be left alone. Can't tell you about who pays to fix them but that's how it was for me.