If you did read first topic it stand buffers and couples and locomotive slippers.
Well i know this result to fault on the track.
I am not surprised.
Märklin provided by self that we test every models before arrive out to the market...

I toke close pictures of the Märklin wagons and you can see how tight it is to buffer to buffer.
The curve tracks are 2231/R2.
If TS friend did really bought a train set that cost € 1700 i am pretty sure Märklin are carefully tested expensive products before to leave the factory?
By the way other locomotives do also show up slippery on the curves like steam locomotive S 2/6.
Design flaws or too weak locomotives?
Wagons at minimum length 282 mm are difficult in the narrow curves while driveway.
S curves??

Goofy seems to be on another planet. The vast majority of Märklin's long coaches run fine on R1 (and the odd S curve), even the Big Boy can run on R1 - though it's not recommended by Märklin.

If you use a mix of other brands you may encounter problems. Problems that can often be solved by changing wheel sets and/or couplers. Sometimes non- Märklin locomotives will have coupler mechanisms that can't swing enough from side to side (don't know the correct words in English) and they will derail the cars in S curves. If you can extend the coupler (or find another workaround) this problem will be solved.

The old style couplers (like the Relex type and "Bügelkupplung" (what's the English word?) usually make a good distance between cars and coaches but in curves and downhill stretches they can fail and make the cars come too close to each other resulting in derailments. The Märklin close couplers do, as the name implies, couple cars relatively close to each other but the important thing is that they keep the cars in a firm grip and at a solid distance preventing buffers getting entangled or cars getting derailed. My own experience has been that other brands and makes of cars and locomotives can have problems with Märklin close couplers, and I have found that Roco Universal couplers (Roco 40395) are a great alternative, they offer a bit more distance but keep the firm grip.

Sorry for the long rant - and I'm not trying to pose as an expert.

Might be better to start another thread on couplers and s curves. We have not heard again from Drongo or friend so I am not sure that what we are now talking about has anything to do with the initial problem which for all we know could be solved.

I alway hope, naively perhaps, that someone at M might read this forum to see what their loyal customers think of their products in which it seems perfectly reasonable to mention it when a product is found wanting. That doesn't always have to mean that something is broken or wrong, but that there is something about the product that could be better.

Probably time to lock this thread. If the OP or any other member has anything worthwhile to add to the discussion, PM the moderators and we will consider unlocking the thread so that you can post.