Ok, just did some googling on the Ender. It has NC endstops (normally closed). That was a bit of a surprise.

What this means is that the disgnosis (that an endstop was permanently triggered) was likely correct, but the cause was much simpler – likely a broken wire.

In an NC endstop, the sensor is always closed, with the pin pulled to ground. When the switch is toggled, the circuit opens, and the pullup makes that pin high. If a wire breaks in an NC endstop, it has the same effect as when it is triggered and acts as a failsafe.

Phranch, once you get the board and screen working again, I'd look closely at the wires to your endswitch. Assuming that the Ender 3 is running NC endstops, then it's likely that the wire or connection is dodgy.