Xubuntu 16.04 Window / Fullscreen issue

[subsoap]

From a tester

First off, it was set to fullscreen but in a windowed mode about 1/4 my laptop's resolution. I unchecked and checked "Fullscreen", and the game changed to fullscreen. After restarting the game, it was marked as fullscreen again, but still in a much smaller window, same as before.

This is all on Xubuntu 16.04, so I'll give a try on Xubuntu 18.04 when I get the chance after I finish work later tonight.