Hi Radison,
I'm sorry to hear your EOS R6 keeps hunting for focus. There are a few things to check. The first are some settings on the camera. Have the camera in either P, Tv, Av, or M movie mode and press the Menu button. First go to the first page under the AF tab and double check that Subject Detection is set to People. It would also be good to have Eye Tracking enabled to help with the face detection. One other thing to check on this page is to make sure Movie Servo AF is enabled.
Next go to the third page under the AF tab. First check the Movie Servo AF tracking sensitivity. If that is set to the + end of the range the camera will prioritize being responsive to movement closer and further from the lens and will keep checking the distance. If it is set to the - end of the range the camera will prioritize sticking to the subject you have selected. The further to either end of the range it is set the more the camera will prioritize sticking to a subject or checking the distance. In a case like this you would likely want to set it to the - end of the range.
The other setting to check on the third page under the AF tab is the Switching Tracked Subjects option. When that is set to 1 the camera will prioritize the selected subject, but if it loses track of that subject it will check for a new one. If it is set to the 0 the camera will prioritize staying on the subject you detected as long as the subject is in frame. If it is set to 2 the camera will prioritize switching to other subjects depending on shooting conditions. In this case it would likely be best to set it to 0.
Once you've dialed in those settings take some test footage to see if the same thing happens. If the issue continues we would recommend attaching a different lens to see if this is specific to how your RF50mm lens and camera work together, or if it is happening with all of your lenses.
