How can I fix my Hotpoint First Edition WMA II washing machine?

Please help! I'm at my wits end. You know the 3 blue plastic bits that fit on the inside of the drum, well they keep shearing and coming off. I've been paying £20 for replacements and fitting them myself but it's fine for a while then I hear them rattling about with the washing again and on inspection they've sheared and come out again! There's nothing mechanical that can be happening, it's just the blue plastic bits that fit into the inside of the drum. The electrical repair shop has no idea what on earth could cause this unless I was washing huge loads or trainers or that, which I'm not. I'd be gratefull for any input.