A few weeks ago, the main body of our Zodiac Barracuda Manta G3 pool cleaner detached from the section attached to the hose.
We screwed it back together but it unscrewed itself again yesterday so I Googled the problem and found this answer on a pool forum.
"That happens a lot with the old G4 cleaners by Zodiac. I have had it happen to one G3 on my route. The threaded area gets stripped. You can’t really see it with your eyes but it is stripped enough not to hold together any longer. That part is about 1/3 the price of a new cleaner…
“I just use duct tape on it and the cleaner works fine. Tape the nut and problem is solved. The tape will wear off in a few months and just re-tape it. Of course the cleaner is meant to swivel right at that point so try not to tape it too high up. The G3 is being retired by Zodiac this year and replaced with the much superior Zodiac T3.”
I have wrapped pink plumbers tape around the thread and it screwed back together very firmly so hopefully that is the end of the problem.