Opera crashes if <thead> has .visually-hidden class when traversing <table> with VoiceOver. .visually-hidden class can consist solely of the following four CSS properties for it to cause Opera to crash:
width: 1px;
height: 1px;
overflow: hidden;
position: absolute; /* or float: left; */
I reported the bug to Opera but unfortunately they don't have a public bug tracking system. 🤷♂️ The only way to "track" the bug is to "take a look in the changelogs to see if it was fixed already".
Update: the bug seems to be fixed 🎉 in the very next build even though they don't mention the bug in the changelog.