How can I fix low resolution photos on iPhone XR?

Ben Waddington wrote: … iPhone Xr, current IOS 18.5 My phone suddenly started producing blurred and low res pictures! When I open one on my Macbook, the resolution is still low, making me think it cannot be a storage / space issue. Or can it? Deleting hundreds of photos does not solve. An old phone, so has anyone experienced the lens just stop working after a few years? Other functions still all fine.

It sounds like Photos may have lost contact with the original picture files. Can you give us more information?

• What model is your Mac?
• What OS are you using on the Mac? 
• Are you using iCloud Photos to synchronize your devices?
• Do you have “Optimize Storage” checked in Photos’ Settings
• On our Mac, where does your Photos Library reside-- in the Pictures folder of your internal drive, or on an external drive? or on a network? on iCloud drive?
• In our Mac's Photos' Settings>General, do you have "Copy Items" checked?

Have you tried restarting the Mac?

Have you tried a Re-start in Safe Mode? This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this: 

           Start up your Mac in safe mode - Apple Support