Can you share some more info that might help us understand and investigate the issue...
- What device model # and iOS version are you using?
- How much free space does your device have when you check iOS Settings > General > About?
- Is this with photos you have just imported from your camera roll or SD memory, or are these with photos that are loading to your device from cloud storage? Are you on WiFi or cellular?
- Are these large files like Raw photos?
- Does it help if you un-install and re-install?
Thanks for any additional info, steps, etc you can share!