Security "Reset" When Prod is Copied to Dev

That is likely happening because your security framework in your PRD environment is not in sync with your DEV environment.  The security framework (users & groups) exists outside of each application database in an environment.  So then when you copy an app from PRD to DEV and in PRD you have used security groups in an app (as your screen shot above) in PRD that do not exist in DEV, they will show up as "(Not Found)" in your DEV copied app.

I am not 100% positive of how to resolve.  You could open a case with OS support to get the steps but I think one option is you can extract your security (groups specifically) from PRD and load to DEV before your app copy. That way when you do copy the app from PRD to DEV, the groups that are referenced will exist in the DEV environment and get associated when the app is copied over.

I think there may also be a way to copy your security framework database from PRD to DEV too.

Again, your best bet may be to open a case and search OS's knowledge base articles for the steps to resolve.

But this does not surprise me if your security is out of sync that you are seeing "(Not Found)".