Maybe we are getting down to some ideas!
I think I've found what looks like the same panel and connections as in your picture and the drawings I found. Compare pic one and two as what you have?
I think F6 is the problem, correct?
Then in the third pic, I did some markups on getting the panel out. Looks like three screws going up, probably out of sight, to hold the top of the metal but maybe some adhesive/sticky at each edge?
I would first try to see if getting the screws out and any sticky loose will let the panel swing out far enough to get behind. Looking at the last picture which is the view from back, it looks like all the lines go off to the right as pictured (left from front) and "maybe" you can swing it for accesss.
Care not to bend too hard as it appears to be PVC or CPVC which are semi-rigid plastic as they will bend some but don't want to break them!
But the bigger problem is likely to be the faucets as it takes some disassembly . If you can't get to in to fix what you find broken behind the panel, then much of the front items have to be removed to get the whole panel out of the way.
To remove the faucet if it has to bedone, I would expect some way to get the handles off, maybe just pull off, set screws in the edge or a top cover hiding a screw in the center of the handle? Then under the handles, likely a nut of some sort to remove to get the bonnet/cover off and finally down to remove the body nuts holding it to the metal. Much guessing there!
This may be a place where it's like cancer and you have to keep cutting back until you get all the bad stuff out, so having the right tool to cut in confined space may be worth a lot. One I might consider is a PVC cutter as it makes it simple to snip a good connection, instead of sawing and leaving a rough edge to deal with as you solvent weld the new parts in.
Do some reading on the solvent weld thing if not done it but it is actually pretty easy if you do it good and through on prep work. Just a fancy name for glue?
See if that gets anything moving?