"when ign is switched off they just stop"
All cars do that, did you mean when you turn the wiper switch off they just stop?
With ignition on and wiper switch in the off position then power should still be coming down the fast wipe cable to power the wipers to the park posiiton. Then the park switch, within the wiper motor should cut the power.
If there's no power (or intermittent) being supplied to the motor when in the fast wipe position then the fault is in the switch, connectors or wiring. If steady power is being supplied then the park switch might be faulty.
Sorry just talking generally here
How about the flick wipe because that uses the fast wipe cable line? Does it park properly after using that or is that the same?