I've been taking at a studio that has no contracts non-fraternization clauses or any of that other stuff. You just buy lessons, and so long as the lessons are good, the students keep coming back for more. Over time, I've taken lessons from probably half the instructors in the studio -- some men, some women. Each brings their own perspective and their own special skill set. Some were definitely better teachers for me than others. But the thing is, no one minded that I was taking from different ones as it suited me. The attitude of the studio and the teachers was that they're all professionals and the customer is an adult and can make their own decisions about what to do, when to do it, and with whom to do it.
Now, I do know that some teachers, especially females who do Pro/Am, get upset when their top male student decides to work with another teacher -- there aren't a lot of top males wanting to do Pro/Am, so the female instructors really want to have a good one -- but that didn't come into play in my situation since I'm not a guy.
If you're curious about the new instructor, see if you can book a short series, like three lessons, to try this person out. You'll know then for sure if you want to switch, or if your current instructor is a better match for you. And if the teachers get insulted about it, then they aren't professional enough to keep their own feelings out of the way and look at what is best for the student. Back when I was doing Pro/Am my teacher encouraged me to take lessons from whoever I wanted, whenever I wanted. He was supportive of me as a dancer, not just as an income stream that he had to protect.
As far as backtracking goes, good instructors who are teaching sound fundamentals won't create this problem. You might go in a somewhat different direction for a while, or take a somewhat different approach, but you will still get to your end goal.
