That's a coaxial (two sets of main blades) ?

Most likely the ball joints and/or pivot on the flybar or upper blades are binding. Sometimes the plasic develops a burr or sometimes gunk just builds up over time. Inspect and clean (rubbing alcohol) and I scrape off the burrs with an exacto knife. There should be close to zero resistance in the flybar. Don't use 3in1 or wd40 up there, If you gotta lube, get some silicon spray and use just a tiny bit - I never had to lube mine up there.

The flybar might be bent.

If the blades are damaged, replace them.