Yes, if there are glitches the 7850 stdi should pick them up too
Can your HDMI source output UXGA, not just 1080p, and see if that has problems?
Looking closely at the 7850 TX lines, they dog bone out to a via then drop down to G2, then run to the 7626. These runs loop around some vias. These loops cause impedance problems which show up more at higher resolutions. Data channel 0 appears to be the worst offender and it also carries the sync tokens. This maybe causing the problems
Note the RX lines seem to be very clean