Minimize, Maximize/Restore, Close buttons not working in Mint 19.3 (so probably also Ubuntu 18.04)

[orbitalchicken]

Platform: Linux Mint 19.3 / Ubuntu 18.04

Nuclear version:

Latest

Description of the issue:

The Minimize, Maximize/Restore and Close buttons, don't work on Mint 19.3 (based on Ubuntu 18.04). However, these buttons work on Mint 20.3 (based on Ubuntu 20.04). So, I'm pretty sure that Ubuntu 18.04 is also impacted.

When I click on these buttons, it does nothing, nothing happen.