If you are meaning the loading fin, it is a common issue - with the C clip that (should) hold it to the cylinder nozzle pinging off fairly regularly - especially if you fill the mags to full capacity. It can be permanently resolved by using a brass C clip manufactured from a 'slice' of an old inner barrel, or the best solution is to use the aluminium Airsoft Pro L96 AWS loading plate, carefully filed to shape/size, and paired with the Airsoft Pro C clip (annoyingly they don't come with the plate). Look up the Airsoft Lee Enfield group on Facebook - all the info on there.
If you are meaning the rear of the bolt itself was wobbly, this is again common, but very easy to resolve - the fake 'hammer' at the rear of the bolt needs to be removed to access the allen head bolt underneath - tighten, with a bit of locktite added. Again, details/videos in the facebook group.
Worth the effort to get the gun shooting reliably - they are superb fun, and pleasingly accurate.