I have met the same issue with the following URL: Oracle 12c: ORA-01792 but not in Oracle 11g
I think it is actually an Oracle bug, but I haven't had "Support Identifier" to login Oracle Support to submit a bug, how can I know when or which release this issue will be fixed?
Or how can I contact with Oracle by email to track and get some information about this issue?
If you do not have a support contract, it really doesn't matter when it gets fixed because you won't be able to get the relevant patch anyway.
If you do not has the support identifier then also you can get the info but those will be restricted.
Also, as listed by EdStevens you won't be able to download the patches without Support identifier.
To check the information you can check our website www.oracle.com, which provides some information.
Example: Here are the known issues about a product: