At work I have had numerous times new tires not needing any weight.. and like you I added weight spun it again to see if it needed weight, which it did.. so trust your equipment.. lolI bought this balancer about 2 years ago in hopes that the hub Wheel unit was working ok. I have been dying to try this on the MG wheels because I installed them myself and I wanted to balance them on the Hunter unit. Well last night I finally got a chance to try it out. The wheel spinner barely reached the tire and I had a hard time keeping it up against the tire. After all was said and done it showed zero weight needed. I had my doubts so I spun it again and move the weight to so see if it moved up the scale and it did. When it did it started vibrating out of balance. So either the wheels are needing zero weight on both sides or the hub ain't worth spit.
sorry to bore you with the long video but I hadn't used it since 76-77 and it was live footage of me trying to use it again.