When changing the mirroring policy Additive -> Complete Mirroring during synchronization, an error occurs:

Error message: the server returns an error
HTTP status code: 400
Response headers: {"date"=>"Fri, 22 Nov 2024 12:49:08 GMT", "server"=>"gunicorn", "content-type"=>"application/json", "vary"=>"Accept,Cookie", "allow"=>"POST, OPTIONS", "x-frame-options"=>"DENY", "content-length"=>"118", "x-content-type-options"=>"nosniff", "referrer-policy"=>"same-origin", "cross-origin-opener-policy"=>"same-origin", "correlation-id"=>"40fb66ca-2f0c-4223-a374-a99d1f10af62", "access-control-expose-headers"=>"Correlation-ID", "via"=>"1.1 server.local", "connection"=>"close"}
Response body: ["Cannot use 'retain_package_versions' in combination with a 'mirror_complete' or 'mirror_content_only' sync policy."]

How it all started:
After synchronizing the repository https://cdn.redhat.com/content/dist/rhel8/8/x86_64/appstream/os
an error appeared on the clients:
Updating Subscription Management repositories.
Module yaml error: Encountered two streams with matching NSVCA ant:1.10:820181213135032:5ea3b708:x86_64 but differing content
Module yaml error: Encountered two streams with matching NSVCA scala:2.10:820181213143541:2b79a98f:x86_64 but differing content
Module yaml error: Encountered two streams with matching NSVCA subversion:1.10:820181215112250:a51370e3:x86_64 but differing content

A solution was found on the site about changing mirroring: https://community.theforeman.org/t/two-streams-with-matching-nsvca/35115/15