The Guy who makes these is aware of this thread and has said that any "defective" X-blok should be replaced by the retailer. If you are having problems then get in touch with MRS who distribute them in the UK. The "defective" block will then be returned to him for inspection. As he said, and this is also my experience the X-blok does last longer and is much more resilient than the standard Chain tensioner block The design allows the minimum amount of metal used to be protected within the block. If you want to PM me with the retailers name, (don't post it due to forum rules), I'll pass the details to the maker.