Potential Solution to the Steam Overlay pop ups.
While I was playing Brick Rigs, I pressed shift and what I thought was the Steam Overlay popped up. I tried fiddling with the settings but nothing worked. I noticed that other people were having the same problem as me and I believe I found a solution.

Discord has a very similar overlay system to steam, however, the default key bind for the overlay is the SHIFT key. I was able to fix the overlay issue by changing the key bind in Discord. If the overlay issue persists I can't help you, this solution just worked for me.