"Does it
1) synchronize the input (2 d F/Fs that must be identical for each channel to make the signal move forward."

yes.the AB signals are synchronized and up/down and clock signals are derived from them

"2) base the up/down on previous and current state."

exactly

"3) do you have schmitt triggers on the encoder inputs"

no - 75175 gets encoder signals

"4) is the inverter drive and the encoder logic on the same board"

there is only DAC output to the inverter and encoder input from the motor on the same board
inverter is seperate equipment

"Have you tested whether the real statement is 'mptor running' or 'inverter active'?"

either or
when the inverter is on the motor is driven ,and 4029 chips are unstable