Controller battery voltage cutoff

The Morningstar Charge Controller has the following cutoff points:

For gel batteries:  14.0
For sealed batteries:  14.15
For flooded batteries:  14.4

The high-end controllers have equalization capabilities.

John

 
I have a PV system in a mountain cabin in So CA.  I have run into a condition that I can't seem to fix and need some answers if you can help.
 
I use a Trace 2400 watt pure sine inverter/charger, six 75 watt PV panels and a Trace C40 solar controller.  Recently I changed batteries.  I was using Trojan flooded cells (390AH 6 volt L16) arranged as a 12V system.  I upgraded to MK 12 volt gel batteries with about the same capacity.
 
I carefully adjusted the I/C and the C40 to the correct bulk and float charging voltages for gel batteries.  The C40 was adjusted with a digital voltmeter at its test points and the I/C from its menu settings.  The I/C is left in search mode while not being used (this can be several days).  The batteries reach their float voltages but then at some point the I/C gets a HVCO fault and displays an error.  The high voltage cutout value is set at 14.5 volts.  This fault (according to the Trace I/C manual) should reset automatically but does not.  My questions are:
 
1. How can the battery voltage rise above the float level and reach the high  voltage cutout point?  Is this characteristic of gels?  It never happened with the flooded Trojans.
 
2.  Why doesn't the I/C reset when the voltage drops lower than the HVCO.  When I get there to inspect things, the voltage of the batteries is about 13.6, well below the HVCO of 14.5.  The C40 at this point indicates fully charged batteries.
 
Any help you can offer will be appreciated Thanks