Hi Gamolina
Here, French Märklin fan.
I have had 2 CS2 since 2010 and 2012. One failed (early version w/o the galvanic insulation) and was repaired by Märklin so both are 5A, galvanically insulated 60215 units
One of these 60215 did just what you describe: instead of having the green arrow displayed in center sceen when the progress bar is its middle, the arrow is never displayed and the progress bar goes all the way to the right.
This has been happening a few years ago. I managed to solve the issue by stubbornly rebooting the unit, close to an internet access and when I succeeded having a full boot, I updated the unit.
Following this I was safe for a few months but it occured and now refuse to boot completely.

This is a way to fail for CS2s that is very common (occured to many owners)
Märklin does not repair the CS2s
A mass memory chip used in the CS2 could be the root cause. It has some resiliency against record failures but past a certain point, it cannot cope correcting its errors.

Except what I mentioned above you have 2 solutions:
- send back the faulty unit to a Märklin shop and obtain a discount on a CS3 or CS3+
- search for the best price of a CS3 / CS3+ in a shop in Germany. This is what I did because the rebate offered by Märklin wasn't good enough. I purchased a CS3 60226 because I had a Link88 already (o I didn't need the simplified Link88 inside the CS3+.

Cheers
Jean

Hi Gamolina
When my CS2 failed I called the Märklin service in Göppingen
- they asked me to send the CS2 for "inspection". It turns out to make a reduction offer on a CS3 based on catalog prices in Germany which is not very competitive
- because of EU laws, Märklin cannot charge for any repair as this would force them to give a warranty
- M cannot warrant the CS2 because some components are unavailable

Train Clock
Yes this feature is not on the CS3 but what good it is if there are no fonctions to take advantage of it.
I am a Rocrail user (and big fan) and there is a "train clock" to start schedules at a specific time (or also in relative time (durations really)
Here is a view of my Rocrail-operated layout (with relative shedules and "Aquarium" mode) at the time using a CS2 and now a CS3


Because of the much more powerful and easier-to-use fonctions, I don't use the CS3's events
CS3's events are way more powerful than those on the CS2 but still lack the key thing: It does not know which loco is where making impossible to do all the things available in Rocrail

But still the CS3 is a very good machine
Cheers
Jean