U2715H not working, but U2713HM does

Hello

I have a facility that uses the U2715H display for video editing and media production applications.  In one room we are using an Extron Displayport switch to toggle between two high resolution sources.  The switcher works fine with "last years model" of 27" Dell display (the 2713HM) but does not play nice with the 2715H.  We've already swapped out the Extron switch with another switch to rule that out.  Any ideas?  Any firmware updates available?  Help!

Thanks