issue using both add_fixed_in_frame_mobjects and TransformMatchingTex

Nobody has claimed this yet.

I have an issue when displaying a LaTeX equation in a ThreeDScene using add_fixed_in_frame_mobjects , and then trying to update the equation with TransformMatchingTex.

The initial equation displays perfectly, but there is a glitch when updating the equation.
The updated equation is first displayed on the (x,y) plane of the 3d scene, then disappear, then correctly displays on the frame like it should, but without the smooth transformation expected by TransformMatchingTex

```
self.add_fixed_in_frame_mobjects(eq3.shift(DOWN*3.3))
self.play(Write(eq3))
self.wait()
self.add_fixed_in_frame_mobjects(eq4.shift(DOWN*3.3))
self.play(TransformMatchingTex(eq3,eq4))
self.wait()
```

Is it a known issue, or am I doing this incorrectly?

Thanks

Start with a minimal ThreeDScene reproduction using the shown add_fixed_in_frame_mobjects and TransformMatchingTex sequence. Compare the behavior of the initial and updated equations, and consider the issue done when the update stays fixed to the frame and performs the expected smooth transformation without appearing on the scene plane.

Written by the indexing model from the issue text.