Its sounds like you chain is the wrong size or your rear wheel is not in the right spot. This sounds like an easy fix. First lossen your rear wheel but don't take it off. (just a little) Keep your chain on the gears as if you were riding your bike and pull the chain with your rear wheel as far back as it will go and then tighten it. Then take it outside and take it for a spin. This happened to me a while back with make nsx dyno. I rode it for months even it skipped alot. I thought it was something major but once I took a look at it is was easy and make sure the chain was tight and was not allowed to move as much. Best of luck to you.