When to make adjustment to the Amount of Pressure:
If you find that the fabric will slip when the presser foot is down,
you need to increase the pressure on the presser foot.
If the fabric is held so tightly that the feed dog is unable to move the fabric,
decrease the amount of pressure on the presser foot.
If it is too tight you will see fabric puckering. I had a machine recently that suddenly puckered fabric. I knew that machine worked. I had put on a new foot - made in China - I compared that foot to an original. It was a hair or two higher so putting on more pressure. I don't know if you can wear out feet that way or not but the new one was puckering and the original was not. The original had cosmetic issues.