Problems i have with this browser.
1. flash and HTML5 isn't very responsive, (buggy broken etc,) 2. sometimes the browser randomly closes, and you can't open it again untill you close it with task manager
What version of Vivaldi (snapshot) are you using? What version of Windows?
I have not read of anyone having random shutdowns for quite a few versions.
TP 3 is well behind the curve at this point. You want to install ver. 184.108.40.206, which you can find at the Vivaldi Team Blog https://vivaldi.net/en-US/blogs/teamblog