Ok I think this now looks quite well solved.
As @Chillbo wrote you may have to restart mediacenter for the options to take effect which may explain why your disabling didn’t had a negative impact
That’s exactly right, I think!
The options under the CEC adapter that are neccessary to set to have this working properly are these:
- Switch source to this device on startup: on
- Devices to power on during startup: TV
- Devices to power off during shutdown: TV
- Send “Inactice source” command on shutdown: on
- Put devices in standby mode when activating the screensaver: on
- Wake devices when deactivating the screensaver: on
Deactivating or setting one of these to a different state let the whole turning on/off of my TV not work anymore. After every settings toggle of the CEC adapter section, the Vero 4k definitely has to be rebooted! 
Thanks for this thread 
I have the same CEC settings chosen as Wuschel with the following exception.
Wake devices when deactivating the screensaver: off
This prevents the TV from being powered back on with any button other than the Power one.
And for transparency, yes, I was restarting the Vero with each change during troubleshooting.
Cheers,
Robert
Ok… Well, in my use-case I’d like the turning on/off of my TV to behave exactly as if this was the screensaver. So, for this scenario the setting should be set to: on
But not everybody wants to have it this way, of course… 
Just briefly reviving this topic for the potential benefit of others…
I had almost the exact same problem happen when I replaced another media centre with a Vero 4k. In this case with a different TV (I added the TV brand and model information of the first incident to my original post). This time it’s with a Panasonic 39" LED TV model TC-L39EM60.
I plugged everything in and configured to my liking. I had turned on CEC control in the TV and enabled CEC in KODI, choosing the same settings detailed earlier in this thread. Being a budget TV there appears to be no remote button pass-through to KODI, so I’m back to using a FLIRC. But relevant to this discussion the TV nicely turned off when the KODI screensaver kicked in. Perfect!
Disconnected my old media centre, did some housekeeping around the stand, mounted the Vero on the back of the cabinet etc. Plugged it all back in and… nothing. No screensaver -> TV Off function. Oh, YEAH! I fiddled around as before but here are the steps which worked this time. Note again, all CEC settings were already the same as the previous time I encountered this.
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Turn off CEC in the TV menu.
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Power off the TV, wait a couple minutes, power it back on.
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Turn off CEC in KODI and reboot the Vero.
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Turn on CEC on the TV.
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Turn CEC back on in KODI and reboot the Vero.
Job done, it works a treat again, as has continued to work through a number of TV on/off cycles and a Vero reboot or two.
Hope this helps someone in the future.
Cheers,
Robert
So I got curious the other day and set the CEC section of KODI to turn the TV back on when the screensaver is stopped. However this only half worked. If I use the OSMC remote I can use any key to turn the TV back on as expected. However, using the normal TV remote, no key will stop the screensaver and thereby turn the TV back, with the obvious exception of the Power button.
If I use the TV remote to turn the TV on after OSMC has turned it off, all is well - I can navigate KODI perfectly with the TV remote (CEC commands working fine) or the OSMC remote.
If I use the OSMC remote to turn the TV on after OSMC has turned it off I can navigate fine with the OSMC remote but NOT with the TV remote. CEC functions seem to be asleep. I have to use the TV remote to turn the TV off and then on again before that remote can navigate KODI.
Cheers,
Robert