This isn’t a really major issue, but it will once there is more avatar variation and with transport systems (especially with fantasy critters such as dragons): Please make sure that the rendering can be defined that something is a head through vertex groups (forexample do not render “Head” vertices if in first person). Similar occurred during @philip 's live demo at SVVR 2015 when he was riding what ever thing it was.
This comes if you head happens to move far enough, or if your head is long enough for it to happen. Here is an example:
earlier this didnt happen as much as the camera rotated with the head.