I too see empty tabs from time to time and haven't been able to reliable reproduce this.
There are some other users reporting this already, including me, but still not possible to finally nail it down.
In my case, when I get empty tabs, I get this solved either switching the location of the tab or by pressing F5 to reload the content, although this does not always work either.
Maybe your steps will finally solve this riddle 
And for reference:
https://resource.dopus.com/t/almost-all-opened-tabs-became-empty-tab-after-a-system-reboot/52556
https://resource.dopus.com/t/my-lister-tabs-become-empty-tabs-occasionally/52993
https://resource.dopus.com/t/tabs-are-empty-in-do-13/52615
As a side note: When quickling switching from one tab group to another (I've set up buttons with appropriate commands) it occasionally happens that a second instance of DO opens with the new group and there I frequently get empty tabs. This is reproducible on my side.