Discussion from IRC:

[14:55:24] <mprahl> jkaluza: This PR https://pagure.io/fm-orchestrator/pull-request/1351 introduced the bug mbooth described.
[14:55:41] <mbooth> mprahl: Shall I file a bug?
[14:55:59] <mprahl> mbooth: Please do, but we need to fix this ASAP.
[14:56:44] <mprahl> jkaluza: get_reusable_module calls get_base_module_mmds which returns all the Fedora platforms in the ready stage.
[14:56:58] <jkaluza> mprahl: yeah
[14:57:39] <jkaluza> mprahl: we should probably not call that method in case when allow_only_compatible_base_modules is False
[14:57:52] <jkaluza> and simply use the buildrequire platform module in this case

I retired 6377 and 6376. I have a proposed patch sent to @jkaluza that I'm awaiting approval on before hotfixing production.

I filed the following releng ticket to retire the other errant modules:
https://pagure.io/releng/issue/8789

MBS production was hotfixed around 14:20 UTC.

PR is up at https://pagure.io/fm-orchestrator/pull-request/1410

Looks more promising now, thanks for the speedy fix!

E.g.:

https://mbs.fedoraproject.org/module-build-service/2/module-builds/6401
https://mbs.fedoraproject.org/module-build-service/2/module-builds/6402
https://mbs.fedoraproject.org/module-build-service/2/module-builds/6403

This issue has been migrated to Fedora Forge:
https://forge.fedoraproject.org/koji/mbs/issues/1409

Please continue any further discussion there.