[musicman691]

While an AC adapter itself doesn't usually go bad the connectors on them can fail. Actually the connection of the wires in the cable start to fracture even with the strain relief provided. Molded connectors tend to be amongst the worst. I've lost count on how many cables with molded connectors I've had to replace.

The reasoning I'm looking at the power supply is that depending on the chip(s) used that connect to the FW connector with no power to the audio interface the computer could be seeing a dead short or very low resistance that the computer's power supply can't handle.

BTW I noticed something in the original post and while it shouldn't have any bearing on the shut down issue I have to mention it. The op is running (or trying to) run PT 12.3 on Mojave. PT12.3 was only considered compatible by Avid for a max of early El Crapitan (OSX 10.11.3).