Virtual switches X10 not working anymore

[gschmidt]

Hi,

Domoticz Version: 4.10545
RPi3b+ with Raspian Stretch

I have a couple virtual switches of the type Lighting 1, X10 ON/OFF which since a few days don't work anymore as they should.
The Switch Icon is not visible anymore (also when I create a new switch of this type)
I also have virtual switches of the type Light/Switch SelectorSwitch, which don't have this problem.
Did already clear the cache of the browser but this doesn't help.

Somebody any idea what might be the problem?