When I was sewing on Wednesday I noticed that the stitch length would change if I put even the slightest drag on the fabric. Adjusting the amount of pressure on the foot did nothing to change it. I did change from the marked needle plate back to the standard one. That helped some. The marked needle plate is a bit thicker than the standard one so the feed dog height was compromised when using that plate. It certainly did FEEL as if the feed dogs weren't high enough. So I found my feed dog height gauge in the change jar. Sure enough, they were too low.
Adjusting the feed dog height on the 201 is pretty straight forward.
Turn the machine over so you can see its underside. Identify the feed dog drop thumb screw. Just above that is a screw. Loosen it. That will allow the whole feed dog mechanism to move up and down. Using your feed dog height gauge, set the feed dogs to the proper height and then tighten the screw. Easy Peasy.