If you type "Bill & Ted" into the search box and hit Enter, you get what you'd expect...Bill & Ted's Excellent Adventure and Bill & Ted's Bogus Journey as the top two results. But, if you type "Bill & Ted" then arrow down to "Bill & Ted's Excellent Adventure in Movies" and hit Enter, only "Bill" is searched for.

This happens with any search with an ampersand, and it's because the search URL isn't URL-encoded correctly when picking from the list.

In the first case, the URL is: https://www.themoviedb.org/search?query=Bill+%26+Ted

In the second (picking), the URL is: https://www.themoviedb.org/search/movie?query=Bill & Ted's Excellent Adventure