Short version (can provide more information if wanted) we have a display (TFT with TTL driver) that we control via PIC32 and Epson Display IC. The supplier changed their driver which should have been a drop in replacement, through some troubleshooting and testing we found the reason it did not work on our system was a capacitor we have on the clock line going from our driver to theirs.
Unfortunately there aren't any notes as to why that capacitor is there, my assumption is noise mitigation, or emissions mitigation.
Layout is Clock out -> 27 ohm resistor -> 27 ohm resistor and a 100 pF cap connected between them to ground:
I'm guessing the new display is just more sensitive to voltages on the clock, so I'm not too worried about that being the reason it works. I'm just not sure aside from emissions testing how I can confirm that capacitor is for noise mitigation rather than emissions.