I am having the same issue and I can't find a commonality in the returns.  I have self employed who didn't get enough RRC, some that received too much RRC and the correct amount of RRC and also straight up W-2 clients with the RRC being correct, over and under.  The one W-2 client told me today his was off by $161.13 and has worked for the same major corporation for many years, so I know we didn't miss anything. His first RRC was short, so I suspect the IRS adjusted it further, but why isn't ProSeries picking this up?

I had only one return that when I went back in ProSeries had detected a change or update so it highlighted the difference since it was filed prior to an update.

The other part that is hard to pin down is that I suspect these clients are getting paid interest since the amount include some change so I can't tell exactly the amount of the difference and the interest.  

I am shocked there isn't more on this topic in ProSeries and it is embarrassing and difficult to tell clients 
"I don't know".

I only had one client get a letter from the IRS and it was very general about the change and we still don't know.  He is well below the limits for his RRC to have been adjusted.

Waiting on letters from the IRS--I guess???