Switch matrix issue. Have you worked on the game at all?

I would get under the game and start carefully looking for a diode that broke off a switch or something miswired on a switch.

Is it just the left flipper that triggers the switch or does any vibration do it? I would start with taking the glass off, put the game into switch test and hit the playfield with my fist a few times. If the ramp switch triggers from vibration during that, most likely the opto transmitter on the ramp is flaking out and should be replaced.

someone else may have a different viewpoint but if it were me I would wonder about it being a flaky opto switch as Kennywawa suggested and would want to rule that out first. Given what you note in your last post, it sounds to me like something is causing that opto switch to register. Could be the transmitter itself or its connections (would check connectors, look for cold solder, opto boards, etc.). I might try switch test and actually flip a ball and watch the dmd specifically to see if that switch registers When not supposed to. I haven’t had my dredd for long but I know when I got it the optos were a bit problematic. Cleaned all of them well which fixed some of the problems and replaced one which took care of remaining. I do know that from an opto problem I had on my DM that it’s not always just the switch that can cause something like that though. On my DM, I had the car crash opto that would randomly activate and it turned out it was related to a poor connection in another part of the wiring. Someone had taped a couple of wires together and when I fixed that connection all the problems went away. Good luck!

The Left Ramp to Lock opto (sw 63) is the one that triggers the start of multiball. Focus on these and check out the stuff kmann suggested.