Changed gearbox oil from factory oil to Motul... what happened?

I swapped the factory oil for Motul in my BRZ and the first and second times I drove the car, the improvement was magical. It was such a slick gearbox! But from the third time or so after I took the car for a drive, the gearbox went back to feeling kind of notchy again (perhaps not as bad as the the factory oil, but a far cry from the magical heavenly feel that it had the first time I took it out after swapping to Motul). Any thoughts as to why the heavenly feeling went away? I've ordered some more Motul, and I'm going to drain and refill this weekend to see if that helps.

I'd really like to get that heavenly feeling shifter back... the difference between that first drive with the new Motul and the way it feels now is dramatic... it was one of the best feeling shifters I've used, but only on that first/second drive...