@Stephan_B
Still having this issue in Unity 2017.3.1f1
.: EDIT :.
Disregard above as I had the issue of the Unity Store downloading an incorrect version of TMP.
Followed instructions here .
When doing so, create a New Blank scene.
Delete your previous TMP asset folder then reimport.
Once imported, restart unity.
Hopefully, unlike me… It doesn’t RESET your entire projects TMP Text elements, making you type out hundreds of lines over again and adjusting their Rect Transform.
.: EDIT 2 :.
Nope… Definitely still having the issue 
TMP Version: TextMesh Pro - Release 1.0.56.2017.3.0b3 (dll only).unitypackage
.: EDIT 3 :.
Failed to notice ‘Patch’ section in Unity Download area of their site.
Unity Patch Releases