Just to confirm that indeed this does not happen in the legacy version, so apparently it's not a "Windows issue" that could not be solved in EN. In that sense, I consider it a bug.
Thanks for suggesting the workaround, although indeed it can be quite a challenge to find an alternative shortcut combination that is both usable and does not create other issues. But looking at these setting also pointed me to the fact that there is also another shortcut for adding tags: F3 (CTRL-ALT-T is actually for "editing"). In many cases, that'll be sufficient I guess.
