I have digged deeper and now I think it is missing a database entry.
# select * from cp2_content where name like '%1220%';
uuid | content_id | created | updated | contenturl
| gpgurl | label | metadataexpire |
name | releasever | requiredtags | type | vendor | arches | entity_version | locked
----------------------------------+---------------+----------------------------+----------------------------+---------------------------------------------------------------------------------------------------------------------------------
--+---------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------+----------------+---------------------------
-------------------------------------------------------------+------------+--------------+------+--------+--------+----------------+--------
2c96813b72e970f001735bdacb8851c3 | 1588151513954 | 2020-04-29 11:11:53.886+02 | 2020-07-17 10:18:52.424+02 | /custom/1220_Public_Cloud_Module_12_x86_64/1220_Public_Cloud_Module_12_x86_64_SLE-Module-Public-Cloud12-Updates_for_sle-12-x86_6
4 | ../../katello/api/v2/repositories/22491/gpg_key_content | ORGANIZATION_1220_Public_Cloud_Module_12_x86_64_1220_Public_Cloud_Module_12_x86_64_SLE-Module-Public-Cloud12-Updates_for_sle-12-x86_64 | 1 | 1220 Public Cloud Module 1
2 x86_64 SLE-Module-Public-Cloud12-Updates for sle-12-x86_64 | | | yum | Custom | x86_64 | 1897444354 | 0
2c96813b72e970f001735bdacb8851c2 | 1588151503687 | 2020-04-29 11:11:43.642+02 | 2020-07-17 10:18:52.424+02 | /custom/1220_Public_Cloud_Module_12_x86_64/1220_Public_Cloud_Module_12_x86_64_SLE-Module-Public-Cloud12-Pool_for_sle-12-x86_64
| ../../katello/api/v2/repositories/22470/gpg_key_content | ORGANIZATION_1220_Public_Cloud_Module_12_x86_64_1220_Public_Cloud_Module_12_x86_64_SLE-Module-Public-Cloud12-Pool_for_sle-12-x86_64 | 1 | 1220 Public Cloud Module 1
2 x86_64 SLE-Module-Public-Cloud12-Pool for sle-12-x86_64 | | | yum | Custom | x86_64 | 2128759327 | 0
# select * from cp2_product_content where product_uuid='2c96813b72e970f001735bdacb8d51c4';
product_uuid | content_uuid | enabled | created | updated | id
----------------------------------+----------------------------------+---------+----------------------------+----------------------------+----------------------------------
2c96813b72e970f001735bdacb8d51c4 | 2c96813b72e970f001735bdacb8851c2 | t | 2020-07-17 10:18:52.429+02 | 2020-07-17 10:18:52.429+02 | 2c96813b72e970f001735bdacb8d51c6
For those repositories working, I see a matching number of entries in cp2_product_content.