Hey Dan, 
Sorry you’re running into trouble with this!
I’m afraid I can’t replicate the same behaviour on my side, so if the issue still persists after refreshing your browser, can you please send us through a bug report? 
To do this, open the affected file (the doc) and click the question mark icon at the bottom-right corner of the screen.
Then click “Report a Bug” and send in your report - thanks!
Okay I’ll give it a shot. I dont close my browser very often so that could be a reason for this.