Bonjour Frederik
Here are a few observations:
- an update may change your settings (bus length on the LikS88, etc so why not your IP settings )
- some programs search for an IP address and others don't.
- for years I was using CS2. exe to search for the CS2 or CS3 IP address
- near to my layout I have a WiFi router (non connected to Internet) while at home I have a TV, Internet, Phone box connected t Internet through fiber optics.
- on the routeur, if I power up both the CS3 and the routeur, the address will always be the same
- on the TV Box, I have nothing to do to have always the same address even though I have multiple connections (2 TVs, 2 smart phones, 1 train)
- on the hardware side, the female CAT5 CAT6 connectors may be failing (no connection until fully pressed home)
- on the CAT5, CAT6 connection, the latching tongue is fragile and latching may fail
- straight or crossed cables make no difference.

Here are my settings with a CS3 60226)


The IP address must start with 192.168.x;y and is firstly assigned by the router / box using the DHCP command.
For me the connection is mandatory because I use Rocrail. I also use my iPhone to control the CS3 when under the layout to make checks (I have 3 levels of tracks)

Cheers
Jean