[morzh]

Well yes it is the xfmr, there is no other ways to leak.

Again, it is probably benign and is what most radios will have.
I recommended measuring the current just to make sure it is small.
Wouldn't hurt to know it for a fact.

There are two paths to induce the voltage through the transformer: 1) via the capacitance of the primary to the shell which is connected to chassis, and through the capacitance to the secondaries, which then through the capacitors or simply through grounded filaments bring it there.