[NeilMcRae]

I've found the issue with missing thumbnails. If you are getting this its because imagemagick hasn't been installed correctly and has no way to process the image that you are trying to work on.
The program will be exiting with an error message like this:

convert: No decode delegate for this image format (/data/html/www.z4roadster.org.uk/gallery/images/3-1627537269-Z4_E85_RO_maincar.jpg)

Also check that your comments or messages have no spaces in them as that confuses the script.

If you want to check if this is your problem then its pretty easy, but you need system admin to the box that you are using:

do the following:

cd /usr/local/bin [or wherever your binary for convert is]
mv convert convert.old
create a script called convert [vi convert or emacs convert]
#!/bin/sh
echo $0 $1 $2 $3 $4 $5 $6 $7 > /tmp/test2

Then try to upload a file using oakgallery.

Once you have done this you can look at the file /tmp/test2:

/usr/local/bin/convert -geometry 160x120> -comment www.z4roadster.org.uk - Gallery /data/html/www.z4roadster.org.uk/gallery/images/3-1627537269-Z4_E85_RO_maincar.jpg[0] /data/html/www.z4roadster.org.uk/gallery/thumbnails/4.jpg

you should try to run that on the command line and see what happens. If you get the same error as I did above then its because that imagemagick hasn't been installed with all its components properly.

The fix that for FreeBSD is to use the imagemagick in the ports part of FreeBSD, on NetBSD I'm just about to test the imagemagick thats in that section.

hope this helps.

Neil.