Thanks all :)
I've switched to another game/world/household who also had a couple of stuck items, in Sunset Valley. You might be interested to know the 'object reset' was not available to me, I perhaps don't have the required module on my MC. So I got them all to finish what they were doing and stand out the front yard and I did 'reset lot'. That worked.
However, I'm sure they had some paintings in their memories, which they didn't any more. (Paint from Memory). So I think doing the lot reset, probably the sim reset too but I only have the lot experience, possibly clears out the painting memory. They had recently had a wedding and I usually get one of my high painting sims to take a 'memorize scene' picture to paint after that, which they usually have stay in their memory for ages, until the next one I think, although I think as time goes on it might become more mottled. So I got the happy couple to put their formals on and pose with and around the arch for some photographs.
That's all for now :)