Hi Coop
I just purchased this aircraft two days ago and I am having the same issue.
I completed a flight, shut down, park brake applied and chocks (nosewheel), and as soon as I turned off the battery, the plane was rolling away down the apron. (The parking area even appeared to be flat).
When I first tried the plane, loaded C+D, the plane was rolling away down the apron.
It has been more than 12 months since your reply, are you any closer to a resolution?
I do own many other aircraft that have chocks, and they don't seem to roll away.