In both pictures you can see the bolt hasn`t moved, but yet the bolt head is contacting the upper (cap or frame not sure) in the second picture with weight on it. this tells me the frame is flexing under the cap! I would definitely get in there and see what is moving!
I seem to recall frame issues on fifth wheels at the pinbox.
this isn`t as easy as just getting bigger bolts! if it was the bolt head and paint line would've moved with the weight on it, it didn`t.
I wouldn't tow that anywhere. something is ready to let go!