Change of monitor - oddities?

I had occasion to change the effective monitor on my Vero by changing the HDMI to VGA adapter (in order to get audio output).
When booted a ‘face’ with the mouth turned down appeared, then there was a sort of ‘flash’ and normal output appeared.
The output was distorted and disappeared off the screen.
The distortion was rectified with the video calibration (first time I used this - impressed), but the image was even more cut off.
After a bit of thought I selected a lower resolution, which fixed it.
I don’t know whether this is what might be expected - hence this post.
I should add two further things

  1. the same problem didn’t arise when changing identically for raspbmc/kodi 14.1 on RPi model A
  2. I missed the tools like tvservice available on raspbmc
    I should also add that I’m using the Confluence skin (which I find easier for me than the OSMC skin)
    Is there any further detail which would help?