I can´t see if short circuits did happens.
But if this happens i would check first if you did connect micro switch correct?
There is three contact.
The middle is for polarity frog while outsides contact is for feeding power + and -.
If this is correct...
Not sure if you did also changed turnout from DC to DCC by cut the spring off under the turnout?
And solder new wire between outer rail to inside rail before frog?
Did you also isolated inner rail after frog?

Hi, the middle is not for the frog. Still I have troubles. The diagram inside the box is this:

https://www.marklin-user...&b=1&editor=true

That connection make short circuit!

It is correct that you have to use two plastic rail joiners after the frog; but not necessarily right after the frog, it can be at the next rail joint, if that's more convenient.

For some strange reason, PECO does not produce plastic rail joiners for the code 200 tracks; you can either use Märklin or the PECO for code 250 tracks.

None of these looks very good.

If you want a good looking solution, use a 2-component glue, and glue with a bit of distance or even with a tiny piece of plastic between the rail pieces.

The strange line you have circled in red should not be installed !!

Per.