This occurred today, August 12th 2020 at around 11am Pacific Standard Time in my group game with Team Create on. This also occurs in another game, owned by a user, with Team Create on (tested around 6pm Pacific Standard Time on the same day). Afterwards, I tested it with Team Create disabled and it worked fine.
When I weld together unanchored parts, the second part’s position/rotation is changed. Whenever I try to move the part, it just randomly changes the position/rotation again. When I manually put in the position, I get the same result.
I have tested this with the normal part, a union, and a meshpart and still got the same results. As long as the part is unanchored and the WeldConstraint is enabled, the second part is moved into a random position/rotation whenever I try to move it. This only occurs in team create games.
Video of the issue
File
WeldConstraintTest.rbxl (3.8 MB)