Short answer is yes - there are tons of "issues", or more so challenges since as we all know, enterprise tech/apps metrics & contracts are complex.
If you need to ask this question then it likely that many more will follow, you should be exploring reaching out to your Oracle Sales or local LMS teams.
Alternatively, there are many Oracle "License Experts" out there, typically former Oracle employees - be aware of their Agenda though. $ching $ching
Back to your question - not clear if you're talking about pure Oracle DB Licensing (minimum users per processor applies to DB EE and it's 25 NUP per Proc Lic) or since you've posted in OD Ebiz then prob not in which case...
****Look at your contract**** (I heard of a contract negotiated way back that was per "Population of the Island") and take the advice from Hussein, read the info avialable from Oracle, then read again, and maybe again etc.
Now for the downright cheeky plug in... I work for a company who have automated the detection and reporting of all of procs and users etc.