Your post definitely illustrates why you don't want to store the same data (location) in two tables. The whole point to a relational database design is to store such data into exactly one table.
You may not need any field for location in the equipment table at all if you set up either a relationship or portal correctly.
I'm guessing that you have these relationships:
If you specify a sort order for the relationship between Equipment and Rentals that makes the most recent rental record the first related record, you can simply include any needed fields from Locations on your equipment layout and they'll show location data as specified for the most recent rental.
Alternatively, a portal to rentals on the Equipment layout can include fields from Locations. You can specify a sort order for the portal that lists the most recent rental first and then you can check the top row of this portal to see a rented item's current location.