I dont know if its any help but I've got ao similiar problem. No real issue with it but its a lil annoying. Just as you said, it happens after a gear shift and for my case, probably once for a journey (so I'm guess its not really dependent on gear shifting), meaning it only happen once or max twice (rarely) when I'm cruising. Its usually 4th gear or 5th gear (so I'll get it when I'm cruising on highway). Talked to Dan at ERD and he reckon might be the attessa pump but shouldnt be any problem but it might be a start sign of failure etc (not 100% certain on root of problem but just guessing). He told me to note the torque split gauge but dont know if it happens too quickly that I couldnt pick it up or its really not showing anything.
Just a quick description, it just feels like a sudden jerk and it goes away after that. The feeling is like erm... sudden lost of power (not total loss but something like when you're in first gear foot off accelerator and suddenly step on it again) but again its like a split sec feeling.