I'm upset with Apple because of poor programming causing a bug in their software making it impossible to regain the space those messages used even after they are deleted. This effects iCloud and the physical space on the iOS device. Restoring from new or blundering around in the file system is the only way to fix this.
That in itself is annoying. Apple and everyone goes on and on about how great the back up system is but the slightest thing goes wrong and everyone tells you to restore from new.
If I only had true access to my iCloud I pay for even basic access I could fix this in 2 minutes.
Understood. What happens if you manually delete a video MMS then the conversation?