strong capacitive coupling of mains to isolated output of AC/DC converter?
I think I have resolved the enigma about the SPICE model and reality



simulate this circuit &ndash; Schematic created using CircuitLab
C4 and C5 are leakage (virtual) capacitors while the rest is real circuit.
You could be accidentally making ground loop if you connected a scope, which has already grounded shield and PE conductor on C1,R1.