Hi hemi43
CV will *attempt* to keep your actual feed close to commanded feed by rounding or blending. The higher your feed, the more rounding you get, the higher your accel the less rounding you get. The outside corners are probably square(er) because your CAM will most likely have introduced an arc at each corner with a diameter the same size as your kerf width so unlike an inside corner, the outside path is more CV friendly. (the outside arc is like in milling where the *correct* way to do a corner is to "roll" the tool round it). Your start and end is likely ok because starts and stops are effectively exact stop mode (as opposed to CV).
You either have to do one or more of these until you're happy. Increase your accel (if you can), lower your feed, tweak CV params (see CV angle, CV distance, CV feed etc.), use exact stop (not good with plasma) or live with it I'm afraid. This is why the often forgotten quest for good accel is every bit as (if not more) important as the more poular quest for speed.