@tmf pointed out that the EDLC can spill and destroy the PCB, @ritterx suggested that there are two series capacitors inside. We'll see what's inside the damaged capacitor.
We remove the plug with the leads, you can see the electrolyte and the contact to the capacitor inserted into the metal housing, it is a "push-in" connection without additional welding or soldering.
The plug on the other side connects to the metal housing.
In the housing there is another element in a plastic cover.
They are two capacitors connected in series. The housing resembles a button cell. There is a spring-loaded conductive pad between the capacitors.
It's exactly as you predicted, inside there are two capacitors that have leaked. It's good that the whole thing is in an additional housing.
I wonder if spercapacitors are used in a housing such as a button cell?
If so, you can easily confuse such a capacitor with a disposable cell or a battery (unless it has a meaningful marking on the board or a print on the housing).
