Fifth wheel jaws locking on their own?

1972 Chem Leaman got new Macks, first time using Imron paint. ASF 5th wheels, jaw drops down. One driver took a load of cement around 100 miles, unloads part and backs up to reach the other silo. hit the brakes and the trailer slid off...all kinds of nerdy guys with pocket protectors and a guy in coveralls with a big bar spend the afternoon out in the yard with that unit. They were from Mack and blamed the paint...

 

Mine does that sometimes. If just releases from bouncing. No big deal. Now my Trailers doing it sometimes when sliding axles. Main thing is that it locks. If for some reason it gets so bad that handle won’t stay out at all, you’ll have to use vice grips to hold it out, get under trailer, pin just inside of jaws. Take vice grips off and hook it up. Then proceed to a shop.

 

Should be a spring and a tab on the bar. Might want to get the operation checked out, before getting into a jam. Might just need a good power wash underneath on the linkage, and some new grease.