When I started using Typescript (whilst at the time using Scala, Clojure and Python day to day), I ran into soundness issues constantly (daily).
I think I wrote a lot of code assuming that the type checker was sound and could check my abstractions, only to find that it wasn't and it couldn't.
If it were more sound, I would rely on the language to do more checking.
I don't get bitten as much any more, but I'm pretty sure that's mostly because I know what tradeoffs the language is making and I use other mechanisms to ensure safety.
Overall though, getting bitten by the unsoundness is fairly rare , imo.