S&W Model 36 cylinder release problem

[Nauga]

I bought this 36 from an ex-detective who wasn't really a gun guy. It's a no dash from the early 70's. He gave me a handful of +P ammo with it, and I think he may have shot a limited number of them through the weapon over the years.
Well, I took it shooting, and it does fine while firing single action. But when I try to fire it double action, after the 2nd or 3rd pull, the trigger locks up.
I quickly realized that the cylinder release works its way forward and sticks there, causing the lock up. If I push the release back, it works fine.
I took the dang thing all the way apart, and gave it a good cleaning after I first noticed the problem, but it still does it.
Anybody ever run into this problem and / or have a possible solution for me?
Thanks.

 

[MartinS]

Sounds like the spring that keeps that rascally thumb piece all the way back. Part 5227 below, the little inner spring in Smith and Wesson's mysterious inner cylinder world.

 

[243winxb]

If not the spring, the +P loads may have done this >.This S&W M29 had peening of the extractory hole from many high pressure loadings. This pinched the center pin, causing the thumbpiece to not return fully when closing the cylinder. The action will not work unless the center pin has pushed the thumbpiece back fully. To fix, drill out the extractor hole to the correct size. Replace the center pin if damaged.

 

[Nauga]

Thanks for the replies.
I disassembled and cleaned the yoke and cylinder assembly thinking that would fix it. It was very dirty, but the problem persists.
I was thinking a new spring would correct it, but being my first M36, I had some vague idea the spring was located under the sideplate.
Your help is appreciated!