Kadees, even when fine tuned, can sometimes come uncoupled where there is a change of gradient. This happens even more so when the couplers are not an exact match for height, as is the case with a lot of the FCPyF’s coaches.
I think I have an idea that may solve this problem, it involves a small pieces of steel wire, cut from a paperclip, twisted into a loop at one end and attached to each coach and passenger loco above the couplers. These loops would not interfere with the manual operation* of the Kadees, so the shunt loco at Grande and freight cars can still couple to the coaches.
When the Kadees are engaged a small magnet would be placed on top of the loops to hold them together, acting as a back-up for the knuckles to prevent accidental uncoupling. At the end of each run the magnets can be removed before the Kadees are uncoupled for shunting and/or running round the train.
It’s just an idea at the moment. Like many of my ideas it may not work, but if it does it’ll save a lot of swear words during running sessions!
* Footnote. I do not use the gladhand tails on Kadees and rely on manual uncoupling using a barbeque skewer, this magnetic back up method will interfere with remote operation using track magnets and the gladhands.