A lot of flight model changes were added in the latest beta. I haven't seen issues with aircraft rolling if the brake is on, but with the brake off and engine at idle they are moving a lot more than they used to. Are the gates on any sort of incline? That could affect it.
If you do not have any custom scenery or plugins installed, please file a bug report with more specific details as I could not reproduce this with the Cirrus at gate A39A.