Any suggestions about a workaround until this is investigated and fixed would be much appreciated since I need to create a functioning fork at this time.

If you need the package that has been omitted from forking only as a build dependency for another package in the new forked repo, then the easiest solution would be to use the "Additional repos" to make the original (unforked) repository available during builds in the new (forked) repository.

If you need the package to be actually present in the forked repo so that users can download it, then the best would be to rebuilt it there. Srpm from here: https://copr-be.cloud.fedoraproject.org/results/managerforlustre/manager-for-lustre/srpm-builds/00739394/ can be used.

If this would be difficult for some reason (e.g. build lasts 5/6 hours), I can copy it manually to the desired location for you.

The linked copr https://copr.fedorainfracloud.org/coprs/managerforlustre/manager-for-lustre-devel/ is not a fork, which means I cannot properly investigate the issue. I guess something was changed from the time the issue was reported. Please, reopen the issue if you can create another reproducer.

Yes, you are right. manager-for-lustre-devel is now a clone that i created using a script to create and rebuild all of the packages from it's origin, due to this issue and our need to have a functioning repo at the desired name.

I've created a new fork that reproduces the problem. In particular this build is a 404 - Not Found. There are very likely lots more but I wanted to point you at at least one so you didn't have to hunt yourself.

Yes, you are right. manager-for-lustre-devel is now a clone that i created using a script to create and rebuild all of the packages from it's origin, due to this issue and our need to have a functioning repo at the desired name.
I've created a new fork that reproduces the problem. In particular this build is a 404 - Not Found. There are very likely lots more but I wanted to point you at at least one so you didn't have to hunt yourself.

Thanks. Well, it wouldn't be that difficult hunt given that https://copr-be.cloud.fedoraproject.org/results/managerforlustre/manager-for-lustre-forktest/ does not even contain epel-7-x86_64 directory, which means all the forked builds are 404. Would you like to reopen this issue?

Indeed. Reopened. I hadn't noticed it got closed.

This is a bug in the forking algorithm after https://pagure.io/copr/copr/c/b15e4504c176c043c7260fd2dacc602ebe2079f8?branch=master

Fixed by https://pagure.io/copr/copr/c/81500106dfbfd2845b92262edde4374f8f49ed78?branch=master