Problems with cinemachine group composer

I'm seeing a problem when using the group composer in our game, we are using it to frame 2 AI controlled creatures that are fighting within an arena. Most of the time it works wonderfully, but sometimes (about 1 time in 10 runs of the game) it makes severe rotations to the left or right that don't correspond with the group transform, and sometimes it fails to track the group approaching the camera and then does a very sharp 180 degree pitch rotation to catch up after the group has passed over the camera.
I'm using a virtual camera with a cinemachine group composer component which is looking at a CinemachineTargetGroup with two targets.
All the settings have been left with the defaults, except for the TrackedObjectOffset which is set to (0, 1, 0) as the targets y position is at floor level and we want to aim a bit higher.
I don't have any other virtual cameras active so I'm not blending into a different camera.
I'm using Cinemachine version 2.1.10.
Does anyone have a clue what could cause sudden camera rotation, and suggest how it can be avoided?
Thanks in advance!

 

Thanks Gregoryl, I'll check whether that is the case.
I was leaving the group composer to position the camera, when I tried setting the position manually it felt like I was fighting against the composer positioning.

 

Splendid, that appears to have fixed it, many thanks!