Oh it certainly is, but it's not something that can be fixed easily.
SMF is dumb and just allows you to upload any file, and when it's an image attempts to create a thumbnail at render time (not at upload time), not only does this mean that multiple concurrent page loads will try to generate the thumbnail at once, if there are multiple images on the page, it will do them all at once (which can be slow) and cause a timeout, preventing the database from being updated with the information about the thumbnails.
The core workflow is very broken and fixing it will require overhauling how things work here. Such a "fix" would make SMF incompatible for future updates/upgrades.