I am guessing here but based on
- only when network connected

I wonder if your CS3 was connected to a CS2 at some stage of if you tried to set the "Slave" network info.
And if you may have picked up some of its S88 references.

In your CS3s list of devices, do you have a (legacy) CS2 configured ?
The CS3 might be trying to find it at startup. If the network is down, it knows not to try, but if the network is up it may timeout etc.

Yes, you may say the new CS 3 is a nightmare. But for me it is similar to e.g. a new car. Which you cannot start because you did not fasten your new seatbelts and/or press the break and/or clutch, which has not to be done in your prior car, and so on.

The CS 3 was never announced to be supposed as an update of a CS 2. Member @Tower must have misunderstood something. The CS 3 is a complete new computer with a new technology, e.g. the CS 2 has an 8 bit processor inside, the CS 3 comes with a 32 bit one. So it is much faster as a CS 2 ever has been. This new processor is one basis why Märklin could improve its track plan control screen as it is. Obvious it can only be partially be compatible to the older CS 2 technique.

Once you understand the logic of a CS 3 (indeed not easy and different to a CS 2) you enjoy using it. My problem is that Märklin always belittles everything as easy whereas nothing is easy, if you do not know how to do it. Where it is not obvious which connections and combinations will be affected by setting specific functions and/or features. Also they do not offer a logical manual with an useful index and register, also showing and explaining all possible combinations and modes of actions. Well sooner or later you understand it by yourself using these sections by the trial and error method. I also do not yet have S 88 contacts, nevertheless sometimes I set them up into my track diagram control screen just do get experience, if there is an influence in whatever I am doing. A great help for myself are the iussed Märklin books and articles in the Märklin Magazine about the CS 3.

When I just wanted to buy a CS 2 the CS 3 was announced. Of course I waited till the CS 3 was available. It was almost one year waiting time. But I never was preshaped by a CS 2 and this was very helpful to myself start using and learning a CS 3. Be patient, the more you cursed about your CS 3 now, the more you will appreciate it later on, when you are better used to it. Learning by doing with patient! Oh, I have to consider this sentence for myself too, even not preshaped by a CS 2. So please do not worry, particularly many of the text of a CS 3 is in German and not in your mother tongue, which makes it even worst to you.

This note about a not existing S 88 link in your layout is misleading. I think it is a software bug. Because the German sentence at the end “Diese Nachricht nicht mehr anzeigen.” (Do not display this message again.) is a hint for me in this direction. Why shall you ignore a message, if it could cause serious damages?

Perhaps you may do a copy from your screen, send it to Märklin Service, telling this message looks like a software bug which shall be considered to solve with their next CS 3 update. But do not despair of your CS 3.

Regards

TEEWolf

Umm, no, they both have 32 bit processors, but the CS2 has a single core processor, and the CS3 has a multicore (I think it is quad core) processor, with each core acting as a processor giving four times the processing capability.

Much of the CS3 code is developed from CS2 code. This can be seen when you go digging in the update files.