I hoped Opera GX would fix this, however this problem kept happening since its inception, and I couldn't find anything about this with a Google search, so I wanted to post here to see if maybe anyone else is having this problem and if there is a workaround other than disabling the Search Pop-Up feature. The fact that these freezings are gone on disabling this feature leads me to believe that it has something to do with a bug within this feature (I'm also using Grammarly addon that provides definitions when I double click a word, but I tried removing it and the freeze on highlighting persisted).