I had a "neighbor" roll in to a CG last winter where I was staying. The sites were almost level, but very slightly downhill to the front. He only chocked one wheel. When he pulled his truck away from the camper, the trailer rolled forward the side that was not chocked, and pivoted around the chocked side. Bottom on the jack slid sideways off his wood block, landed on the soft ground and sunk in to where the coupler was nearly on the ground.
I went over with blocks of wood and my hydraulic bottle jack to help him get it lifted back up. Goes without saying someone could have been hurt had they been in the way. He learned his lesson to chock both sides before unhitching.
Safety is first thing...not speed. Take the time to do things right.
