Grand MA Consoles interfacing House Dimmers through a Net2 gateway

I am the ME for the Adler theatre in Davenport Iowa.  The facility was upgraded to a Sensor rack system in the 1990s.  Used the Emphasis System.  The facility recently installed an IONxe (which works great).  As a Road House have shows that bring their own consoles from ETC equipment to Grand MA.  Adler has a node/gateway FOH setup to transmit console info to the House system.  Last night a show brought a full Grand MA for their show.  They brought a lighting package of movers w/separate control snake.  They interfaced the House dimmers through the ETC Net2 node viva DMX line.  Worked with House dimmers all afternoon.  First Act of evening had no problem with House control.  {I keep our IONxe running for House Light control}.

It was reported that the control of House dimmers became problematic a half n hour into the second ACT (main band).  A certain group (submaster) of dimmers did not respond well.  Pop on w/out operator control and not black out.  Erradic!  Had control most of the time.  Other groups/submasters would act in the same way.  Was not individual addresses/dimmers, but seemed to be groups. 

Any ideas of why?  Suggested solutions?  I am going to switch nodes around.  Maybe purchase an Optical ISO interface.  FYI - never had this problem before with multiple shows.  Though this is the first full Grand MA console I have seen come through.  It was just shipped from the rental house to the Adler.