My gut tells me that the problem is in using the cut tool. If I am correct, below will help you. If not using snaps (like snap to vertex) you can sometimes inadvertently create an extra vertex/edge very close to another vertex. This will cause the topology to not be composed of quads (even though it may look like its…
Actually, when viewing you Gif again, I see it is a relic of Cut but maybe not my initial guess. Instead of two coincident vertices, you may also have a vertex just off of the main edge of your strip--creating a five-sided polygon. This is still a result of using Cut and not being careful with the placement. I suggest you…