coats 775 wheel balancer

I purchased a used coats 775 balancer the guy that i purchased it from put a tire on and spun it and showed me it worked and tire was balance the test tire he used had similar weights on inside and outside of rim it was a 15 inch steel wheel.
I brought it home anchored it to the floor put a level on the shaft and leveled it then calibrated it a bunch of times.
Every tire I have balanced so far has asked for a lot of extra weight on the outside on the second spin an example of a tire I balanced today on a 18 inch wheel with clip on weights asked for .1.25 on the inside and 1.50 on the outside on the 1st spin after attaching correct weight at the 12 oclock position on the second spin asked for 2.50 on outside and 0 on insideIf i do as asked it comes up as a good balance.
Any one have any suggestions I have made sure the it is anchored correctly and has no movement. I do about 200 tires a year and had an old FMC 4100 balancer that I have used for 15 years with no issues I wanted to upgrade and get something newer.

I'm not familiar with that balancer - is there an option for static and dynamic? :huh:

Just for giggles, if you start with an unweighted wheel and only give it one side first, does a check spin change the needed weight on the other side? Our shop recently upgraded balancers because the old one liked to play games like yours. I never fully figured it out, but I did get better at minimizing the needed number of check spins to get it zeroed. Weighting one side at a time seemed to help.