Hi Leon,
I just checked with EVAL-ADV7625-SMZ running BF_7625_XREP_X2.2.2REL_20140625.bin and QD780 (not QD780A) as a source and I see 0x26 when output is configured for 12-bit. So it seems there is some difference between your environment and mine. 720p60, HDMI, Color Space = YCbCr444, Format Type = TV.
Can you check your settings?
Also, do you have our software driver source code for ADV7626?
-Matt