Thanks for the help all, no, not tampered with in any way. I dont know how to take these things apart, I've never even had the stock off. I plan on getting the power adjuster locked, but havent done anything about it yet.
Barrel is free floated.
The O ring on the port pops out after each shot, and needs to be pressed back in. Would that do something? Transfer port was giving blow by in the past, but I fixed it with a little silicone sealing under the port.
I'll do a full string and look for oddities
I need to shoot it more, its entirely possible that it will just 'fly' from time to time, and that its not pressure related. Its just last time I shot it indoors it didnt settle until the pressure had dropped, and I've noted in the past that it didnt seem to hit much when filled to 190bar.