Big Picture has been buggy ever since the most recent big update/reskin of Steam.
As someone who actually owns and uses a Steam Link occasionally, the black screens, frozen UI, and other issues have been annoying.
The Big Picture UI that was used for what seemed like years was absolutely outdated visually and needed a refresh, but for me it was bug free and ran just as intended. This new version has added so many bugs that just don’t need to be bugs.