Barrel spacers are actually last on the list of problems. For one, if you've never taken apart the gun, the factory spacers (while shitty) have probably not changed position much since you got the gun. Foam spacers might slide, but as long as your barrel is secured by the endcap this isn't your problem.
Is this a new problem or has it been happening the whole time? My guess is that your bucking/hop up started screwing up on you. This happens with all L96 models, and it happens to clone models a LOT faster. You can try to take apart the stock unit but even with shimming, such a low quality unit will start messing up on you sooner rather than later.
Your only real solution if this is your problem is to replace the hop up and barrel
Is this a new problem or has it been happening the whole time? My guess is that your bucking/hop up started screwing up on you. This happens with all L96 models, and it happens to clone models a LOT faster. You can try to take apart the stock unit but even with shimming, such a low quality unit will start messing up on you sooner rather than later.
Your only real solution if this is your problem is to replace the hop up and barrel