Can Duplicate Files Cause Backup Problems?

I’m preparing to back up my computer, but I’ve noticed I have a lot of duplicate files scattered around. I’m wondering—can these duplicates cause issues during the backup process, like slowing it down, using extra storage, or causing errors? Has anyone experienced problems with backups because of duplicate files? Also, do backup programs typically handle duplicates well, or should I clean them up first? I want to avoid wasting space and ensure my backups are smooth and reliable. Would love to hear your experiences and advice on dealing with duplicates before backing up!