Tried one of the suction and release type 6-7 years ago... the type that "hops" around the pool. It got stuck behind the pool steps and stayed in one place all night. It literally sucked a hole in my liner the size of a quarter. Could not patch properly due to sand loss underneath, so I've had a sandbag there ever since. Thinking about trying again. Recommendations? Liner is 15 y/o.... want to be careful.