Watching the video makes me wonder if there is an out-of-gauge problem with the loco wheels or (and?) the turnout rails. Because the loco can successfully navigate the turnout after it was "fixed", it seems that the loco was at least part of the problem. For the future, you should get an NMRA gauge for your scale and learn how to use it to check both the wheels and rails for proper dimensions. It isn't hard to do with the proper gauge and the instructions that come with it.