This is my last post on the Kitara, just to wrap things up in case any wandering MIDI minstrels stumble across the thread.
I don't know if they'll ever release a new one, but I reckon all the old ones go the same way. If you find a working one, you should be prepared for it to develop screen flicker at some point.
Capacitive touchscreens are tricksy things. I've tried all the home remedies to no avail; I've subjected it to hairdryers, oven lighters, pressure and suction, and none of it has made any difference. The "tails" are hard to handle; no compatible digitisers can easily be found, and you'd need considerable expertise to adapt a different type.

Rebuilding it entirely would be difficult because even the fretboard scanning is complicated, inaccessible and undocumented.
* * * *
I've rationalised it like this. Consider a vintage Alpine White Les Paul. Over the decades, they take on a dirty cream colouration. But nobody minds that.
Likewise, the Misa Tri-Bass takes on its own vintage characteristic, in the form of a defective, epileptic screen. But via the "fretboard trigger" mode, it's still possible to wring some notes out of it. And in a perverse way, I still like it.
The 'button' fretboard implementation makes it possible to play polyphonically on a single 'string' in a way that's not possible with other approaches. But although other button types are available, like the Ztar, the touch-sensitive capacitive approach is nice (even without the sensitivity upgrade; I've given up on ever acquiring the cable) - and it's unique in that respect.
This is a dumb "look it flickers but it still works" demo showing that with a bit of MIDI note filtering there's life in the old dog yet. (The mode that enables you to play via the fretboard also has flickering touchscreen pads playing other random low notes you need to screen off.) Some day I'll do something musical.
https://www.youtube.com/watch?v=KN3LtEhRdKQ