Do the 226 and 229 use the same mag release? If so you could put the 229 mag release in the 226 and see if it fixes it before ordering a new mag release.These are all Mec-Gar which is supposed to be the OEM (I know some OEM mags for these are also produced by checkmate).
Generally the 3 mags that came with the gun don't seem to do it but I believe I did have one of the included mags do it (under recoil) at the only range trip I had. Thought I might have bumped the mag release but not thinking so now.
Also, since the all seem to lock up fine in the 229, I'm generally thinking not the mags.
I'd be awfully aggravated if this mag release is not the culprit and for some reason this gun is mag picky.