I'd pull the yoke screw, and examine the yoke. Not a bad idea to remove the sideplate as well to check the insides.
Hopefully you know how to do all that correctly and what to look for.
The OEM yoke screw has a spring loaded pin that rides in the angled groove of the yoke, aft of the button.
Proper replacement screws are available from S&W.
If you're over the age of 75, a can of Spinach will be helpful prior to offhand range time.
