Did you test any of the inputs(?)… just to see if it results in the same faulty output?
Just off the cuff, i would say: since afaik the A/D converter (TVP7002) isn’t involved in creating the test pattern, the problem is related to the FPGA or the HDMI transmitter IC. The best case scenario is a simple solder bridge or a cold solder joint on the FGPA, the HDMI transmitter IC or simply the HDMI out connector. Worst case: one of the two ICs is broken and needs to be replaced.