A couple of other thoughts.
Is your table level? Does the machine roll by itself in any direction? It may have been level when you set it up but could have settled.
Check to see if any of your cords may be causing drag.
Are you only noticing the drag with round designs? If so, it may just take some practice. I have an older Lenni with no computer or bliss and was struggling to get circles instead of squarcles. Remember, you're trying to make the carriage move in two directions at once - horizontal and vertical. Start your design smaller and work your way up to larger circles. Try stitching out a lower case cursive alphabet (or words or your name) since those "designs" would be instinctive (assuming you can write in cursive).
Ctmax reacted to SueD in Hard to free motion on Millie