My first Duo trailer showed signs of those two cross bolts working, so I drilled a 1/2" hole vertically in that area and installed a grade 8 bolt to hold everything tight. No working thereafter.

I'll so same with replacement Duo/trailer.

Piet Barber has that rig now and he might share pics?

I'll send a picture to Dave who might post it for me. (Thanks in advance Dave!)