Doesn't the 5017 have the backup float sensor? That should shut down the pump and sound an alarm that could wake the dead.
In any case, like rvitko said, IR light could cause issues. It should be easy enough to test though. Get something to block the fuge light from the sensor and see if it happens over the next week or two. If not, you've (likely) found the problem and can find a more permanent solution, like getting the sensor moved into a shadow/dark area or shielding it from the light.
If you're still having problems, you could grab a water level sensor that you set well above the ATO sensor(s) which would cut power to the pump if the water gets too high. I'm not recommending/vouching for this one, it's just the first one I saw on the BRS site, but something like this:
https://www.bulkreefsupply.com/smart-level-security-autoaqua.html