Hi Justin, and welcome to the forum!

It sounds like you may have a faulty or cracked backup valve, although I can't explain why it would begin to work correctly and then stop. The next time it stops working like that, lift the part of the hose that contains the backup valve out of the water and see if it is spraying water. If it is spraying, and doesn't stop after about 20-30 seconds, then the backup valve is likely the problem, and it's about a $75 fix. If it does stop spraying (like it's supposed to), then see if the unit starts working correctly. Have you taken the unit apart to make sure that the belts don't need to be replaced? Sometimes the drive belt will slip off, or eventually get loose--it's a fairly easy fix and about $15 worth of belts at the pool store (the last time I had to replace mine, anyway).