The schematic shows U4 pins 8-10 as an inverter. In TINA it is probably completely different, maybe it is the mixer.
If I remove U3 pins 5-7 won't the display circuit mix the filter outputs all together?
The schematic shows that the
input of U3 pins 5-7 is from one filter. The filter drives only one the display driver, not all of them.
U3 pins 5-7 is shown driving only the input of inverter U4 pins 8-10. Both opamps are doing nothing.
The mixer is not shown on the schematic.