We have a weird setup here too. Wastewater runs to a sump buried in the driveway, then gets pumped to the sewer line under the street.
About a year after install, we had an issue with the sump pump running constantly, so I pulled the lid to figure out what was going on. Opened it up and found a gross mess of cement-like papier mache gumming up the whole thing. Float was jammed up so the pump wouldn't shut off.
The "papier mache" was a gummed up mess of Charmin TP. That stuff is nice to use, but too thick to break down properly. Convinced the wife to switch to Kirkland brand TP and haven't had a problem since.