Need Help Varying pressure on CummaCut D-60U

I cannot get the pressure right on my plotter. It seems to change pressure throughout the job, so it will cut the outside of an "O" no problem, but then the inside of the same "O" will be barely even scored. We just ran a test cut that sampled all shapes, big letters, and small letters; It did okay on the shapes but the letters weren't cut all the way through. Then we sent the job with those same settings and it just destroyed everything, wayyy too much pressure. Is there a setting I'm unaware of, or is our plotter just down for the count? We just changed the blade last week because of the varying pressure issue, but now trying to get the correct pressure is extremely difficult when it keeps changing. Our plotter is the oldest piece of equipment in the shop, so I wouldn't be surprised if we need a new one, I'm just wondering if there is anything I can try before we resort to buying a new one...