I am sorry, but this was a false alarm. Only today did I realize that I was extracting the descriptions from another page than I thought. This other page is a dummy page whose image description fields were indeed all populated with the value "original".
@reems
Thanks to your suggestions I solved the puzzle!
Your mentioning that I was not using repeater_[fieldname] made me recall that I was using a symlink on this template. Turns out symlinks are not followed/not allowed on my web host, Hosteurope.
So after copying the code from the destination of the symlink into the original file, everything was working again.
Thanks again for your help!
Cheers,
Stefan
