Are the EOS switches wired and set properly? If you have voltage, but they are under powered, maybe they are in hold position (open)? BK's are normally closed.
Remember the flippers are serial, so what happens to one flipper on a side will affect the other.
If that's not it...
In vid 4, is the voltage test to the flipper coil? If so, sounds like you have a return/grounding issue since the voltage is good at the coil. Check for ground continuity on your harness? this is why i thought of the EOS switches.
Is your cab grounding connected to the backbox? There should be a wing nut to hold the strap to the bb at the base. This shouldn't be a factor, but check it anyway.
There are two critical connectors for the playfield, the main one, then another to the upper pf. Check those for ground continuity.
Have you replaced or cleaned the flipper switches to make sure you have good contact? Same with the eos
Manual and schematics are here:
Look here for info on the EOS switches if you need -