Thank you for your help- yes everything but L45 was off and behaving normally. And everything is fine with the OEM driver board, thank God. It's the RD board that has the issue. Hoping to tinker with it today with my DMM.
So first and foremost, I found where "Q46" is written on the RD board. It's hidden BEHIND the transistor, I totally missed it.
Second, that one transistor looks darker than ALL of the others, imo. Is that a sign that Q46 is probably the culprit after all? It's second from the top on the first full column.
I also see on the RD schem that the transistors should be FQP13N10L, but mine has IRL520N's, which Im reading might be inferior....