Sony D-NF430 turning itself off before reading the disk

I tried to replace the laser assembly from a donor machine because my main CD player started skipping and stuttering despite the CD and the laser seeming pristine. The donor is a much better taken care of machine with sound issues so I assumed using that ones laser assembly on the older one would be fine.

I get the new laser assembly into the older CD player.

It spins up and the screen cycles the Walkman logo, But right as, or just before, it starts reading the files, it shuts down and stops spinning the disk. It does this with both the new and old laser assembly.

I've checked to make sure all the connections were clean and firm, none of the ribbons or wires are pinched or exposed as far as I can tell, the laser on both assemblies are, at least to the naked eye, perfectly fine, I've put in new batteries, and I've checked multiple CD's that I know should play, only to be met with the same result.