I had found it best to raise the trailamate in the drawbar clamp when towing the van, as I noticed the hydraulics didn't work too well if the unit was laid sideways while travelling.  The other day the wheel dropped down while driving!
The inner shaft is held in place by a small bolt which screws up into the hydraulic ram, but this bolt had fallen out and that let the inner shaft to drop - fortunately it didn't come out of the outer shaft. I found a suitable bolt and used locktight on the thread so it shouldn't happen again!  Others have suggested to have a chain attached to the foot of the Trailamate.