After owning it for a couple years, my holiday trolley stopped auto-reversing. It would leave the barn and when it got to the end (gapped track) it would just stop and not reverse. Today, after experimenting with it, I found that if I ran it at half-speed (or so) or slower, the auto-reverse would start working again. If I slowly increase the speed, there comes a point where it stops doing the auto-reverse. Also of note is that if I run it slow and it starts coming back to the barn, then I increase the speed, the trolley just stops in its tracks.

Any ideas what could be going on? Thanks!