What's the deal with these window regulators??

The rear 1/4 glass on my 65 vert would not move...so I pulled it out, found the crank works fine, but the arms were all bent up...I put them back in the correct position as best I could (used the other side as a guide). Now everything lines up, but after I crank it up and down a couple of times the top arm pops off!!! I don't understand how it is just a stud that holds the arms together...no bolt/clip/etc...Is there a trick or tip to get these arms to stay together...I thought about welding the top arm to the stud...but I don't have a welder...so looking for a fix with basic tools


Thanks!