Did you explicitly grant the user access to the RLC_Class class? In lightning, users must be explicitly given permission to access top level classes for the components in their pages.
This is changed from past releases where implicit access was granted.
Additional information about granting access and the critical update which brought this change can be ...
Related question: Do I need to define sharing for inner classes?
I prefer inherited sharing, with sharing also would be fine though.
if it would be enough to report them as False Positives.
No, it's better to have small number of false positives for the security team to review.
You need to tell your stakeholder that the "Search" requirement is not possible on Salesforce standard functionality yet.
By Default the Standard Account Duplicate Rule & Matching Rule should prompt users on create anyway if there exist a duplicate Account e.g if Account Name & Phone is the same
OR you can just create your own custom ...