First of all try to change theme in:
Main menu -> System Tools -> Budgie Themes
Maybe it's a bug in a theme.
Second. Try to install and test another desktop manager.
The next suggested step is to upgrade to newer Ubuntu version with newer graphic packages and kernel. I've installed my system with 18.04, then upgraded it to 18.10, 19.04, 19.10. In my case I had no issues. But if you have manually installed proprietary video drivers or something similar, you could expect some issues, so be cautious.
Also, the comment by Jerare Yoshi from linked question says:
I had the same bug with another AMD GPU (Radeon HD 5700) in Ubuntu
19.10 (now fixed). So your bug is related with your AMD GPU
This means you could also install fixed graphic drivers.