When using the Content Size Fitter OR the Vertical Layout Group components on the Content of a Scroll View, and playing the scene an error pops up:

Trying to add (Layout Rebuilder for) Content (UnityEngine.RectTransform) for layout rebuild while we are already inside a layout rebuild loop. This is not supported.
UnityEngine.Canvas:SendWillRenderCanvases()

2. How we can reproduce it using the example you attached:
See the attached video.

1. Create a Scroll View add Text GO to its Content
2. Add the Content Size Fitter component on the Content
3. Press play
4. Notice the error. Exit play mode
5. change the attributes of the content fitter: Fit - minimum size
6. play again
7. Notice the content size is now fixed
8. set the attributes of the content fitter: Fit - Unconstrained
9. play again,
10. the content size is still fixed

regression from 5.2.1f1