Hi
We hit this on a live shop: VirtueMart 4.8.4, Joomla 5.4.10, PHP 8.4.26, Linux.
Category pages log "Couldnt create thumb, file not found" for product images that are actually on disk. The stored file is file.JPG. createThumb() builds the source path with a lowercased extension, so it looks for file.jpg. On Linux that path does not exist, and the error is written on every category view.
Use the stored file_url when that file exists.