To Reproduce:

1. Open the attached 'ReproProjTextUpdate.zip' and run 'testScene'.

2. Notice that after ~5 seconds 6 identical exceptions are thrown:

'Trying to add UnityEngine.UI.LayoutRebuilder for layout rebuild while we are already inside a layout rebuild loop. This is not supported.
UnityEngine.Canvas:SendWillRenderCanvases() '

3. This happens anywhere between the 5th-8th update and there are always 6 exceptions, the value seems to be changed correctly even when they are thrown.

4. This behavior is independent from the time period between the updates, you can change the coroutine in testScript.cs to run every frame, it will still happen after similar number of updates.