Just rechecked and it is the same on all 3 sites – (2 Church ones and my Personal site).
I am certain that this was working before, as I recall forgetting to add post-image-head and then setting it in order turn on the image. Perhaps it was working by accident rather than design and one of the updates to WP or the theme “fixed” it.
I have added the code suggested to the one site that currently uses a child theme and that works.
I will now add child themes to the other sites and include this code.
Thanks again for the fast response.
I am now puzzled as to why I did not spot it earlier!