07 vert radio trouble

[Mark75407]

Hi, I need help. I have a 2007 gt convertible. 76k miles. I am second owner. It was stock when I got it. Weekend car for me, maybe 3-4k miles per year.
Had the shaker radio, I upgraded that to a Sony xaxav3250 radio. Had it installed by Best Buy about 2 years ago. No issues since, it’s been great.
I can remember about 2 months ago I hadn’t driven it and I woke up to a dead battery. Used a jump box and was good to go. That could or could not be relevant.
Over the past month or so the radio has lost power. When it loses power the “cure” is to pull and reinstall fuse 56. It will then generally work for a drive or two before having to repeat. It started out as the radio would just not power on when I started the car. If I could pull the fuse and get it on then I was good for the drive. Now it’s twice lost power while driving. Both times I could hear a clicking sound off and on behind the radio for a few seconds after it died.

Things I have tried:
Replacing fuse 56
Replacing the acc delay relay in the passenger box
Removing negative battery terminal for 30 mins
Purchased the same radio new from the store and installed. When I installed it would not power on until I pulled fuse 56 and reinstalled. Then the old radio worked as well. I returned the new one, since it did not seem to solve the issue with the fuse.
I’ve looked at wiring diagrams and I just don’t know what could be causing the radio to lose power and then what could be “clicking” behind the dash afterwards (while the car continues to run, with no other issues, mind you)
All the wiring looked good when I pulled the radio to test the new one. It was taped and zip tied tightly and all connections were secure.

Any ideas?

 

[07 Boss]

I know there is a circuit that cuts power to the radio when the start cycle is engaged. It is to prevent power surges to the system upon start up. I know this because I tapped it for turning my traction control off when I start the car. It's my traction control monkey. That way its off whenever I drive and I can still turn it back on if I need to while driving. I think its better than turning it off in the tune. Anyways, I'm not sure if the bcm controls this or if there is some kind of relay, but if there is a relay there is the possibility that its getting stuck. When you pull the fuse it might be resetting the stuck relay.

I know it's a reach but you seem to have a weird problem. I can't remember which wire it was or where the rest of the circuit is. I guess I could look for the thread when I installed it but then I would have to log on to moddedmustangs forum and I don't think I'm a member anymore.

 

[86GT351]

Look at the diagram. It shows 2 other fuses that are in the Smart Junction Box. Fuse 20 and Fuse 6. Could be a SJB going bad. Look carefully to make sure there is no water intrusion over there. It is not uncommon for the cowl drains to get clogged and then on the passenger side water comes in through the Cabin Air Filter area.