33V residual AC voltage in domestic circuit when switched off? Neutral switching?
It is normal for a typical multimeter to show some low voltage on disconnected wires.  This comes from the capacitance and inductance of the wires themselves.

Since there is essentially no load (the meter puts a tiny insiginificant load on it) that voltage doesnt go away.  But the actual current it could supply is tiny.  It poses no safety hazard and can't shock you.

Some meters have a mode that puts a load on the circuit to eliminate such false readings.  If yours doesn't the easiest thing to do is measure while a load like a lightbulb is still connected.