I have created a new SP List and have a nice working calc equation that scans 4 fields for values and works. i paste that same validation equation into a SP List that was created from a copy (of course updating the field names, and consistent field types and options for both Lists).
The use of this List is to ensure as status is updated from Not Done -> to Inprogress -> to Done, that the 3 associated fields are ensured to have valid information appropriate for each status level.
Applying this validation to the created from scratch SP List works, and when applying to the copied from another SP List does not work.
The source of the copied list is also used in other Power Automated procedures, and Power apps
This really depends on what formula are you using, the type of fields in each of the lists (working and not), and the values that are inserted.
I would start by double checking if the equivalente fields are of the same type in both lists, and after that confirm if the list has any bank/null values. It could be that the formula you created did not contemplate such scenario and could be breaking functionality.