Might be the spring considering its the only part you changed that could affect anything like that. Also I'm not familiar with the P226 but I have a KJW P229 and the stock spring is quite stiff -- first GBB I've owned that I didn't feel needed a spring upgrade, for that matter -- so I'm wondering if the 150% spring set was actually necessary in the 226?
I'd try swapping back in the stock springs and see if it still occurs.
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