Most of the common errors can be disregarded at some point. If you really want to do some research, I refer you to Engineer Manual 1110-2-1416 page D-6 and D-7.
EM 1110-2-1416 (15 October 1993)
The error messages you see can be referenced back to those pages. You can also see when to disregard some of the messages because of other factors.
I am considering putting together an one hour webinar for ASCE on HEC-RAS warning messages and notes. Do you think yourself and others would find that type of webinar useful (i.e. would you pay for it?)?