Imagine a person who is part of a discussion changes the focus by starting a train of thought considered irrelevant and in this manner deviates the route of the discussion into other / irrelevant subjects or tangential comments. You want to ask them to focus on the point of the discussion and restrict their comments to the point at hand.
Bringing up this question I am going to find the closest verb which can be used when you want to ask someone not to "deviate" the topic at hand.
Note: I do not need any idiom. I need a natural verb for the case meaning "deviate". [I don't know whether the verb "deviate" works here by itself or not.]
I found the verbs bellow. Please let me know which one in natural in this sense and of they both mean something else, then please tell me what is the most natural one: