The first thing I notice is that you may have a few dry solder joints so firstly I would try carefully reflowing every solder joint
to do this simply hold your soldering iron tip on each joint for around 3 seconds or until the solder melts making sure you hold your tip on the component leg and pad at the same time to get a good connection remove your transistors from the sockets when reflowing
Some do look as if too much heat has been applied from your soldering iron what kind of soldering iron are you using?
Do you have bypass signal
You should also cut off as much of the component legs as possible on the solder side of the pcb this can cause short circuits if they come into contact with the bare metal of the enclosure, back of the pots etc
We need to clearly see all of the components on the pcb and where your wires connect to on the 3PDT in and out jacks and DC jack a picture like this below is ideal
With a picture like this we can begin checking the values and orientation of the components and ask for more pictures as required for example close ups of the jacks and so on
From your description of whats happening you may have more than one fault but it sounds like you have a dry solder joint causing a poor connection and high resistance to the signal flow