Thanks for the pics, they’re very helpful to see what’s going on. Is the top side of the print head (nipple area where dampers connect) flooded with PiezoFlush as well?
Keep in mind: I’m not a formerly trained “certified Epson tech”, though have been working on Epson printers for [U]many[/U] years, and have replaced/fixed [U]many[/U] parts over the years, so can give you some advice based on my personal experience, but we do not provide formal support for self repair to your printer, so say “proceed at your own risk” and direct people to follow the repair manuals. My advice may or may not help, and I can not guarantee I will help you get your printer fixed, so follow my advice if you wish.
I can see the whole area is pretty wet with PiezoFlush, and the cable connection is definitely wet- this is likely what’s causing your problem.
To access the end of the cable- carefully unscrew the print head from the black plastic carrier, which is starting at step 10 on page 270 of the 7800/9800/7880/9880 repair manual (screen shot included below). Figure 4-110 shows the two ribbon cables that connect to the right side of the print head.
Gently pull the two ribbon cables straight out of the print head connection, and carefully wipe/dry the entire area: cables (esp the ends), connection and surrounding area of the print head (TIP: be VERY careful with the print head and gentle when wiping the metal surface/bottom of the head- and do NOT touch the bottom of the print head with anything scratchy or your bare hands, as oils can damage it), print head holder and around the print head, and bottom of the dampers. You may want to use some canned air to blow out any hidden liquid from inside/around the connection and electrical area of the print head, then let it sit for a few minutes to help it dry out a bit more before carefully reconnecting- making sure everything fits easily and snugly. Do a few regular cleaning cycles after everything is back together, then print a nozzle check to see how things look.
I hope this helps!!