Hi @fkm
After investigating all your files, I'm sharing an update from the dedicated resource team at Autodesk which works closely with the Revit's test engine:
This issue is seen in cases where the font wrapping changes when editing various zoom levels, etc
The new text component in Revit 2018 renders text slightly differently and results in some fonts getting slightly wider and some fonts getting slightly narrower. This is often not noticeable, but in cases where a line of text in very very close to wrapping, the slightly wider font might cause a wrap–which is what has happened in few instances.
To fix it you, can either stretch the box of the text note (or label) slightly to accommodate this and not wrap. Or you can make the text slightly smaller. In the latter case, you can change the Verdana text from 3.000 mm to 2.970 mm and the wrap is quelled.

Changing the font scale/ resolution to 101% is a temporary solution. This may not apply if you have multiple monitor setup.
Let me know if this helps.
Regards,