You have a lookup field in tblScales that uses a field in tblLocations as its source? I didn't know you could do that; probably because like many others, I avoid lookup fields (not lookup tables) and their issues altogether. The more accepted approach is to use a lookup table if you want an easily editable lookup source. Then you would use forms to save the parent record long integer ID (often autonumber PK) into the child record as a foreign key value. In that case, you would be using long integer values to relate records rather than text. Text based keys would require that you use natural keys (real data) instead of autonumbers. So the direct answer from me would be to ditch the lookup field altogether.
I had a lot of links saved but lost them when my hd died, otherwise I'd point you to whatever I had about not using lookup fields. Suggest you see what you can find on it if no one else chimes in with something.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.