When apps like Ubuntu Software and Files are maximised they do not have title bar buttons. I did see Nautilus window buttons disappear when maximized but they didn't find a way to solve it. It just fixed itself.
I've tried disabling all of my extensions and restarting.
Here are my extensions:
- Advanced Volume Mixer by Hatell
- Applications Overview Tooltip by RaphaelR
- Clock Override by .ext
- Dash to Panel by jderose9
- Lock Keys by kazimieras.vaina
- Media Player Indicator by JasonLG1979
- NoAnnoyance by sindex
- Refresh Wifi Connections by kgshank
- Removable Drive Menu by fmuellner
Okay. So I only listed the extensions I had enabled. No Title Bar by franglais125 was installed (but disabled). After uninstalling it Files kept its window buttons when it was maximised but Ubuntu Software still has the issue. After a restart, Ubuntu Software got its window buttons back!