Lightroom Classic Sync settings failing

[Anoushka5F88]

I am editing timelapses and have to sync settings across multiple photos. Lightroom is able to sync owingor copy/paste settings between pictures but fails after a while. Pictures then start showing an error saying

"You wont be able to edit this picture"

Not sure why this happens intermittently.

Version: 10.2

OS: MacOS Big Sur 11.2.3

[F. McLion]

Are you able to manually edit these pictures afterwards?

When you say "fails after a while", do you mean always after i.e. 50 pastings or ...

Does it stop pasting with the error you mentioned?

What type of files are you working with (source, format ..)

[Anoushka5F88]

I'm not able to manually edit these files afterward. All RAW images. Working in batches of 500, ~100mb images.

Pasting stops after some pastes.

The series is 

edit image 1 > copy and paste to image 2 > edit more on image 2 > copy and paste to 3 ... and it stops after a few images as I add more selective edits. 

I see the "processing" spinner rotating on the bottom right but nothing happens and an explanation mark appears on the top right after a while in the footer. Image preview won't load. 
It seemed like lightroom lost the link to the file so I removed the images and synchronized the folder. 
Though this only works sometimes, not sure what the issue is. 

[john beardsworth]

"You wont be able to edit this picture"

Can you do a screenshot so we can see the exact wording?

"It seemed like lightroom lost the link to the file " "MacOS Big Sur"

If the images are not on your internal hard drive, where are they? And can you try moving them there and seeing if you get the same problem?