while waiting for the replacement buffer chip I took the mega board out and connected all with BB wires and some transistor level shifters. could not resist trying this... 
photo
The good news is that the display does work this way!
On the removed, broken 74AHC244 pins 5,6 and 7 were shorted together internally also pins 13 and 14 were connected.
So the cause is obvious although the system is still behaving very strange.
When I receive the new chip, I will replace the mega board also because the system is not behaving as it should.
to be continued!
photo
The good news is that the display does work this way!
On the removed, broken 74AHC244 pins 5,6 and 7 were shorted together internally also pins 13 and 14 were connected.
So the cause is obvious although the system is still behaving very strange.
When I receive the new chip, I will replace the mega board also because the system is not behaving as it should.
to be continued!