I’ve been seeing this as well. Seems to happen with any whitespace character, space, tab, newline, etc.
I’ve just got a project from Staff Member - Kyle Langley (trying to help with a problem in [My Project][1]), and browsing that I found this strange Append which is changing its size very fast between this two state: (It wasn’t easy to capture)
It was caused by the trailing whitespace (one piece of trailing whitespace worked fine, but that node had two).
It would cause a feedback loop whereby the editable text thought it should show a scrollbar, which it did, but then because the scrollbar made the editable text wider than before, it then thought it didn’t need it anymore so hid it again… over and over again. It’s fixed for 4.14 