A CRS related problem may take a long time to be diagnosed and solved.
CRS reinstall is an option when a fast solution is required and none is at hand.
There are different ways to perform this task. This document: How to Manually Remove and Reinstall CRS, describes one way to perform a manual uninstall and reinstall.
In total the process may require a downtime of about two hours, if you have experience with it.
This is one of the processes I've defined to be rehearsed by the DBA team, so they can quickly reproduce it if necessary.