[morzh]

Tim

as you probably understand we do not know what "farthest spring from the front" and the other spring and the "closest to the speaker" mean in schematic turns.

Please try to speak in schematic terms, and give me measurements relative to GND, whatever spring or contact it might be.

Both device turned on and turned off.

You also want to measure BEFORE the spring contact and AFTER to eliminate oxidizing as a possible reason for bad behaviour.

PS> Meantime if what you told means one battery either loses voltage / gets shorted / the contact is oxidized is true (so far I am surmising) we might have a bad transistor. But again, I am absolutely not sure I understood what you wrote so far.