When you had the AJA, did you try to change the settings with 4:4:4 RGB with the AJA software and an usb cable ?
AJA HDP2 manual :
AJA HDP2 HD-SDI/SDI to DVI-D Video and Audio Converter
Color Space—Selects the Video Format. Choose from Auto, 4:2:2 YCbCr, 4:4:4 RGB or
4:4:4 YCbCr. Choosing “Auto” lets the HDP2 automatically select the format
based on the capabilities indicated by the attached monitor.