When you edit the Favorites List containing the System, go to the Options tab and look for a box that says "ID Search" you want that set to Off.
ID Search is a setting where the scanner is "searching" for talkgroups that may not be programmed. ID Search On is to discover new talkgroup IDs. When the scanner discovers a new or unprogrammed talkgroup ID, the number of the talkgroup are displayed where you would see an alpha tag displayed for a programmed talkgroup ID.
ID Search Off is where only programmed talkgroups are monitored.
So you need to confirm that ID Search is Off and then write the Favorites List to your scanner.
The term "ID Scan" (when contrasting it in context with ID Search) is a term that I think Uniden is trying to get away from. They are now emphasizing ID Search Off or ID Search On.
Us old-timers are used to the ID Scan term, when it basically means the scanner ain't ID Searching. Older model scanners (x96 era) used ID Scan or ID Search.
(If you have the electronic version of the manual for the 436, you'll see "ID Scan" is used mostly in a priority context).