3600111 - Group Reporting: Error, when trying to create a new Consolidation Unit or FS Item (Release SAP OP 2020)

When trying to create a new Consolidation Unit in the Define Consolidation Units app (App ID: F4685) or a new FS Item in the Define FS Items app (App ID: F3297), you get an error message, that "Enter a valid consolidation version with a maximum of 3 characters and spaces." even though the version is correct.

SAP S/4HANA Finance for Group Reporting
Product Version: SAP S/4HANA OP2020 with SP level 1 or higher

Group Reporting, Consolidation Unit, create, FS Item, SAP Note 3586968, Define Consolidation Units, Define FS Items, error, version , KBA , FIN-CS-MD , Master Data , Known Error