3500 series not storing fixed-IP address

[Claude-1300]

Good morning from rainy Belgium.

I have installed my home network in fully-cable Gigabit Ethernet.

Every single device has of course a unique IP address.

The one I have assigned to the TV is 192.168.1.52
The Synology Media Server has been assigned 192.168.1.65
The DNS/ADSL modem/router has 192.168.1.254

For a reason I ignore, the TV always resets from FIXED IP to DHCP as soon as I shut it down/restart.
In DHCP it always takes 192.168.1.66
But is is sufficient to click on Fixed IP again in the Setup menu to have all the manually entered coordinates appear - so they still are "somewhere" in the TV.

What can be wrong to make the TV "forget" the fact that I asked for Fixed IP ?

Txs in advance

[Claude-1300]

Problem still the same after resetting to Factory settings and reinstalling the Software Upgrade.