Hi there!
That would make sense to see issues in RH Satellite if they appear in Foreman/Katello, because it’s the upstream for said product 
I don’t remember if there was a EPEL syncing issue a while back, but in the current version I don’t see any issues, so maybe Pulp (the application in the whole Stack that does the syncing) already got adjusted to be able to deal with the changes.
That said, you are on a very old version (Foreman 3.1 → 3.10), so it might be done with updating. (if don’t forget to update one version at a time)