No personal experience.
But I remember reading that this has happened in H0 gauge before. Some folks were using a small voltage for track occupation detection on an automated layout. Some locos with bell-shaped armatures were causing problems as they were crawling slowly while all other locos simply stopped.

Coreless motors have no cogging torque. Electric tricks that rely on the cogging torque or the higher startup voltage of the standard motors may no longer work.

Never heard of them but they do appear to supply a fair amount of stuff. I see the controller can work off batteries which is interesting. They have a help line that might be able to suggest fixing the problem.

That sounds interesting. We’ll have to try that Frank.
Obviously there is a huge difference in power required to move the different generations of Märklin engines. I will post a video first chance I get but with my only new generation Marklin loco just flipping the switch is very abrupt and totally out of scale. I should point out that I have a Rokuhan Shorty loco, just for testing purposes, and it also moves with the Rokuhan throttle closed, but very slowly, not nearly as fast as my new Marklin 88923. But anyway that probably explains the need for a “shorty wire”.
I will also email Rokuhan, they have been pretty responsive to my emails on other subjects.

Hi Ajay:

I sent a message to John to see if his product can work with non-shorty locos simply as a "range shifter" which is all I think the item is. But in all honesty, it's likely just a resistor that makes the range more coarse so it should be able to work with any locomotive in spite of the warning on the item product pages. It's just that you might, for some locos, then suddenly not be able to feed enough voltage to get them running. In thinking on this a bit more, it likely will not help the zero point on the RC-02 being too high with your specific locomotive.

I have already done a demo of the new controller:
https://www.facebook.com.../videos/581063885560012/
You simply press a button on the controller and it shifts the range from coarse to fine. Again, it is slated for September 2019 release.

Back home and playing with my trains again :)
I will now try to upload a few videos. Here is the reply from Rokuhan, note that they were concerned that I might want compensation, I did not ask for that at any time, I just wanted them to see the effect and comment, so it is all good there.

Dear Mr. Eric Schellenberger

Thanks for your reply.

1.Shorty motor car no stop with RC03/RC02 at throttle dial position Min.
This is unexpected result.
We released RC02 on 2011 and RC03 on 2013 based on existing loco spec.
We have no plan to release shorty series at that time.

Shorty has light weight and used same motor unit with existing Z gauge motor cars.
As result, Shorty can be run less electrical current than ordinal Z gauge locos.
And we found some shorty motor chassis doesn't stop at throttle dial position Min.
of RC03/RC02 because of less current consumption.
Therefore we suggest to fix direction switch on center if shorty no stop at Min position.
And we have RC004 controller for shorty.
Sorry for your inconvenience matter and please understand.

2. New Marklin loco no stop at Min potion.
3. Oval track get power only from RC03

We understand your new Marklin loco doesn't stop at Min. position of RC02/RC03.
However do you have same problem with existing old Marklin controller or not ?
Frankly talk, ROKUHAN controller are designed based on ROKUHAN locos.
And we fixed controller spec. as ROKUHAN locos get best performance.
We are not sure new Marklin loco motor spec. and others.
However we can understand new Maklin loco motor has good performance
and required less electrical current.
But we can't have responsibility for RC02/RC03 function with new Marklin loco.
Please understand our position.

So we can send only above reply at this moment.
Please understand and let us know if you have unclear matter.

Best Regards
ROKUHAN support

obviously uploading videos to this forum is not the way to do this...

If anyone can tell me the proper way to post videos (preferably from Vimeo) that would be great. I think you should be able to play the video without going to the Vimeo website via links but I don't know how to do that...

Yes
I have experienced no stop with my 2 new br80s (0-6-0) and rail bus with the rokuhan controller.
And, i have experienced older 5 pole locos going into high speed when sharing the same track with the new motors. Dont really understand why, but it does happen. Almost like tripling the voltage to the 5 pole while the new motors still crawl.