@Arnold D. Cribari this may not be an appealing solution but I bought a used Legacy b6 and that pesky tether would go out every third turn. I ended up buying some of the Loctite Ultra Gel control glue. I plugged my tether in and then very carefully added a dab of glue to fireman and engineer's side of the tether. I mean tiny dab. You can't even see it without a flashlight. That tether hasn't come apart since then and I've moved it off the track multiple times. It's a pain because you're stuck with an attached tender but it makes things able to run and it could be taken apart if you scraped the glue dab off with a flathead screwdriver or razor blade.
I haven't had to do this on my 0-6-0 yet but I also don't have any tight turns to run it on yet. It's destined to work a short stretch of track that will have tight turns though so maybe trouble is in my future.
