I have seen it happen with our club CS3+ but no other and have used two other CS3+. mfx locomotives have a DCC address and a mfx one. The mfx one must be unique as the CS3 assigns it. I wonder if your mfx loco has the same DCC address as another loco? Our club CS3+ has well over 200 locos registered so a duplicate DCC address is a possibility. It is possible to list locos by address but not sure if you can soecify DCC address. Perhaps if you turn off the mfx feature.

Hi
Why needing to register anew ?
This is typical of an MFX loco not fully registered (other protocols MM2 and DCC do not have registration)

What to do about it?
Simple: you pose your loco on the programming track and let it register fully and you are done.
Once the loco is registered anew, (at the begin of the loco list with a red oval symbol instead of a full one) Switch to edit loco mode, select the loco and start editing - changing parameters) and after a while validate. The loco should now return to its normal position in the list and the red oval tage (low center screen) is now ful / plain). The loso is not anymore listed at the list's begin but where it belongs (sorting by address or by name)

Notes
In the Märklin world MFX has the top priority and with default factory settings the CS3 will use MFX protocol with MFX capable locos and simply ignore other protocols.
Märklin decoders will also ignore other protocols (your CS3 is multi-protocols by default) if MFX signal is present and if the MFX protocol has not been inhibited on your loco.
A good practice for all new locos is to make their registration on the programming track as on large layouts with many locos and long cabling, the registration may be not so effective.
The use of the Ethernet plug (I use Rocrail with a lot of data exchange) may pollute a clean registration so unplugging it during the registration may help


Cheers
Jean

Hi Jean

First I must admit that with a new mfx locomotive, in recent years I have simply placed it in front of the place with CS3 and let the registration happen there and not on the registration track!

And I have even made small adjustments with sound and such in the same session.


Since you always provide good, well-thought-out advice, the following happens:

In the future I will change that so that everything happens on the registration track but with my age etc. there will be many more draft animals for the system.
There is actually only one planned, and it is a Frichs Firkant with a Loksound 5 decoder, which also works as mfx.

So in the future I will try to follow your recommendations to use registration tracks when it comes to:
• A new locomotive
• When a "random" locomotive is updated when CS3 is started, it is now via registration track
• When there are changes to the decoder

And then I have to start noting which mfxs have been that way, to see that there are no repeats. But it takes time, so it will probably take 6-12 months, so I have to remember to come back…….