And I encountered also that bug on the previous version I guess 2.8. I can't remember actually but as per mentioned you only have version 2.6.3, so..
You should update your electrum to its latest version which is 2.9.2 if I'm correct, that's the issue of previous updates of electrum.
EDIT: it's 2.9.3 the latest version of electrum
It's doing it on my newly installed Android one as well unless that's regressing back to its previous version?