The Roco close couplers have a notorious habit of uncoupling at the start/end of inclines/descents. The Maerklin couplings are better, but can open if the little tongue on the bottom contacts the centre studs. The Roco Universal close coupler has a similar design to the Maerklin one. I find them more resistant to manual uncoupling than the Maerklin ones. The Fleischmann profi couplers seem pretty good, but likely have similar flaws to the Roco close coupler.
Have you considered trying the NEM version of US Kadee couplers? You could also try using fixed couplers for every pair of coaches/cars, which will lessen the risk, while still leaving the consist capable of being easily uncoupled.

If you find a spot where the train uncouples, look for signs that the foot of the coupling is touching the centre rail stud, or for a change in incline of the rails. In many cases, the coupling problem can be alleviated by reducing the incline at that spot.

regards

Mike C

I find Kadee couplers are generally very reliable, In shunting my 2-rail layout I have not had any trouble with them. However, Care needs to be taken that the steel pins on the bottom of the couplers clear the contact studs on Marklin points. With light wagons it can be very spectacular to watch a wagon being launched into the air after a trip pin catches on a contact stud... After adjustment they should be fine.

The advantages are that they couple very lightly, so you don't have to ram the wagon at a scale 50km/h to couple up. They uncouple with a magnet under the track, which means they are not compatible with the Marklin uncoupling tracks. However, using kitchen cabinet door magnets you can put an uncoupler pretty much anywhere you like. Wagons can be easily lifted out of a consist like with the Fleischmann close couplers, which could be handy.

Disadvantages are that they are not as available in Europe as the European brands, they uncouple when the grade changes drastically like Fleischmann couplers. They are also not true close couplers so there may be a gap between wagons.

Kadee couplers for wagons with NEM shafts are #16, #17 and #18 (short, medium and long respectively). I am not too bothered by the gaps between wagons so I tend to just use the #18's because they will work on anything

Cheers,
Rick

Hi!
If inclines are not laid carefully. No problem if they start/end smoothly.

Besides Close Coupler and Universal Coupler, Roco also offer another coupler: the imitation of the automatic prototype coupler. It has no moving parts, but plastic hooks that snap in with a click. No automatic uncoupling possible, but I presume they would be rather good for a layout with permanent operation. Number is Roco 40376 for a bag of two. Trains can still be uncoupled by hand for maintenance.

IMHO the Roco Universal Coupler is more reliable than the Märklin Close Coupler. With the latter, the metal loop does not always move freely. Sometimes you have a pair that will always uncouple - if you swap two cars or turn one car around, the problem is solved.
Never had this sort of problem with the Universal Coupler.

You can probably use fixed couplings between the waggons, and then a magnet between loc and consist. Yes, the idea is from Lego-trains... ;-)