I'm running oXygen XML Editor v 22.0 on Ubuntu 19.10 with the Cinnamon desktop. I've noticed a little bug in displaying open tabs in the editor - with more tabs open than the editor width allows, the rightmost tabs aren't displayed and there will be a space between the rightmost visible tab and the dropdown menu (see screenshots), erroneously suggesting that there are no more documents open.
Here's a screenhot that shows the actual open documents - note that some appear to have no tabs:

This made me think that I had no more documents open to the right:

But hitting the right arrow gives me the next open document:

I thought I had mistakenly closed many of the open documents until I hit the open documents dropdown list and realised that they were still there.
This behaviour appears to be new to version 22.0, possibly because the JVM is new.
As always, thanks for a great editor!
Best,
/Ari