Welded parts are not being rendered during tweens, when the game window is minimized

Parts welded via Motror6D to the tweened part, are not being rendered while the game (or studio) window is minimized. If the tween is complete before coming back to game, parts are rendered in wrong place (when they were at the moment of minimizing) Bug occurs also when switching to script editing without stopping game. The tweened part itself does not express this behaviour.

The bug happens 100% of time, unless tween is not complete when coming back to game. When another tween start playing it “repairs” rendering.

To reproduce the bug, you have to tween models with very popular in community “root” method. Anchored, transparent root is being tweened, while unanchored model parts are welded via “Motor6D” to the root.

Here is reproduction of the bug.
minimise bug.rbxl (18.8 KB)

After launching the place, please wait a while, then minimize window for 20 seconds, and go back. Notice how some of the blocks are rendered out of place and unselectable.

This bug happens on Windows 7 64-bit machine (SP1 up to date). I am unable to test it on other platforms, but it seems that mobiles are unaffected, since you can’t “minimize” the window on android, and the game just quits.

It happened in my game “Crazy Stairs”, as I use this method to move stairs around.

I use NVIDIA 650TiBoost card, but i checked the bug on the other pc and specs seem irrelevant. Also players reported this bug while playing my game.

As far as I know the bug has been there for a while (at least few months), but I always figured it was something I am doing wrong.

There is a workaround i am using now. I am temporarily setting the transparency to 1 and back after each tween, to force the engine to re-render the parts.