Western Airguns Western Sidewinder S Air Leak

I took my Western Sidewinder S .25 out the other day to shoot it. I filled it up to about 275bar - my normal amount - and on the first shot, I heard a louder than normal pop and then all the air started leaking out the magazine area and the barrel. The gun was in semi-auto mode. It drained all the way out and will no longer hold air. Clearly an o-ring blew, but I have had no experience with working on the Western airguns and really don't no where to start (other than just send it to AoA for repair). Can anyone that has had this happen to them and have fixed the problem give me some direction? What's funny is that it seems trouble runs in 3s... this is the 3rd gun I have now that went to hell in a hand basket all at the same time! Thanks.
 
Talked with Sean @ AoA and he said that it may not be a blown o-ring, but either a jammed pellet/slug or an incomplete firing that prevents the magazine from forwarding correctly to the next position and then dumps all the air out of the barrel. I was able to fill it up again and tried firing and it is back to shooting correctly. He said the cause can be a slug with too small a diameter. I put the JSB Mk2 Redesigns back in and worked like a charm.
 
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