Discharging also requires a few go's,... don't believe it's discharged because you 'just did it'....the capacitance of the tube will partially restore a charge, so in effect, you might measure 20kv, then 10kv, then 2kv after each discharge-recovery........

Personally i keep a spare grounding plug (actually a scrapped EHT (aquadag) cap) permanently connected to avoid the residual recharges.

P.S. ELECTRICIANS know LESS than NOTHING about electronics hehehehehehe  ;-)

MM