This is an example of a problem using the "tab" keyboard button when creating a line : http://demo.ovh.eu/fr/e751cd65d9776ab1efa4de5b17199dcf/
Is it a known problem ? The current solution is to use the horizontal "too thin" horizontal scrollbar.
It's funny that you mention this as I ran into a similar problem while doing some data entry the other day inside the data browser. I will open a Jira ticket against this issue. While it's not "harmful" it is a bit of a jarring experience to think that you just lost all your data.
:D. Please tell me when this will be fixed.