Both shows should have the year in the show folder (at a minimum)
They really should have the year in the episode titles, but it’s not always necessary
To further guarantee a match you can use the TVDB or TMDB show id.
You can take a look here of how to do that
https://support.plex.tv/articles/naming-and-organizing-your-tv-show-files/
Show folders like this
Battlestar Galactica (1978) {tvdb-71173}
Battlestar Galactica (2003) {tvdb-73545}
After you make the naming changes you may have to Plex dance ← click
