Also, can you send me a picture of the other side of the preamp card? We noticed that the pickups were hardwired to the board, which is OK, but need to check how they are connected now.
Can you plug in the bass with the backplate off like in the pictures you sent, and then touch each pot individually and let me know if the sound is the same as when you touch the backplate?
Other things I noticed in the pictures is that there is a ground wire connected from the ground flag of the 1/4" jack to the backplate, which is OK, but it's not original.
How long have you had this bass and what is the service history since you had it?