This happened with P3D V4.5 with the PMDG Boeing 747-400. I have had it happen on three separate occasions where, upon being asked to release the parking brakes by the ground crew, the plane gets launched into the air. In the first video, this takes place at KATL gate E2, scenery by ImagineSim on December 19th. Once the parking brakes get released, the plane gets launched 1,000 feet into the air.
https://www.twitch.tv/videos/1683342996?t=2h59m28sThe next two videos take place at RKSI gate 10, scenery by PacSim on December 31st. This happened within seven minutes of each other. In both instances, the plane gets launched 20 feet into the air.
https://www.twitch.tv/videos/1694106318?t=7h10m52shttps://www.twitch.tv/videos/1694106318?t=7h17m38sOddly enough, this video takes place at RKSI at gate 10 on December 25th with the same airplane, yet no incident here.
https://www.twitch.tv/videos/1687682959?t=22h34m40sIn the case of the Atlanta incident, I did not manually undock the jetways. In the case of the Incheon incident, I did manually undock the jetways. Not sure if there's any relevance, but thought I would point it out anyway. I have also attached the aircraft's gsx.cfg and the configuration for the two airports in question. All of them are custom.