Looks like the edge of your hammer is getting caught on the inside of the blowback unit when the slide is being returned to battery.
Do you have a 150% hammer spring in there? If so, just as a check...swap it back to stock and see if it goes away.
Also...when it's stuck...if you reach in there and gently pull the hammer down a hair...does the slide continue forward?
You can polish the part on the BBU that it's catching...and/or the tip of the part of the hammer it's catching. I've re-beveled a couple of hammers to fix this. Doesn't take much...just take a close look at it when it's catching to see what angle to change it to.