[Machine gets hung up move during ruler work]

Curious if you ever found the cause. I am currently working on a quilt and having this exact problem!  I do have a ruler base on the machine but going in a straight line I get ‘hiccups’ and just as you describe, it’s a fight to keep it straight. I feel like I’ve checked everything and still can’t figure out why the machine is doing this. 

[stitch quality on back of quilt]

Have you found an answer to this issue yet?  I am having a very similar problem and it doesn’t seem to resolve no matter what adjustments I make.