Makes me wonder if the mechanic might have added 'his' secret' ATF additive? 
Or, could it have been an electrical connection in one of the solenoid connectors that just happened to make good contact at the same time the ATF was changed?
One drain and fill causing that first problem almost immediately and the last drain and fill fixing that problem almost immediately . ???
Lots of 'IFs'
Buffalo4
PS: Very happy to hear that it is working well now. If that 'other' ATF is still suspect, I would surely do 3 more drain and fills.
Or, could it have been an electrical connection in one of the solenoid connectors that just happened to make good contact at the same time the ATF was changed?
One drain and fill causing that first problem almost immediately and the last drain and fill fixing that problem almost immediately . ???
Lots of 'IFs'
Buffalo4
PS: Very happy to hear that it is working well now. If that 'other' ATF is still suspect, I would surely do 3 more drain and fills.