Help - KJW G23 not blowing back correctly.

I've recently started having a few issues with the KJW G23 (I've had it for at least two years without any issues what so ever) Lately, it will only shoot around two three shots, and afterwards it will stop racking the slide, looks like there isn't enough gas to make it blow back.. I've tried other mags, but the issue persisted, I then upgraded the knocker on it, and still the same issue, I cleaned it as well, and lubed it from scratch. Here's the issue - https://www.youtube.com/watch?v=oDqbftYV2Ak In the video it isn't evident but If I rack the slide again, sometimes it resets and gives me one good shot, but rarely, it usually will just shoot again with very low force. Oh! I've also checked the mag and it is does still contain plenty of gas in it. Help!