I agree it makes no sense but it does depend HOW the ATF was changed. Correct service procedure (correct me if I’m wrong here as I’m 80 based but cannot imagine the Collie would be any different.) is to undo the drain plug and allow what comes out to drain. This is probably only 1/4 of the box contents. Some folks drain from the radiator connection which doesn’t drain the prescribed amount. We had a chap on here in Oz do this just after buying a 105 (I think) and had similar symptoms to you. It corrected itself over time. This doesn’t mean yours will do the same but it’s a hydraulic system that’s not designed for total fluid removal. It is possible the system has become airlocked in some way. There is also the possibility that there was a different ATF in there from the P.O., such as fully synthetic. Any foam caused through the ATF being churned around and not flowing fully can then have adverse effects on its ability to pull clutches etc in fully, or to allow the TC to function as it should. Hence the need to monitor the level of the ATF if it’s been over drained. I think first of all you should drain the box from the drain plug and inspect the ATF that comes out. Burned with traces of metal would indicate bad things have happened. If need be Karl’s offer of a box would be a solid route to go.