Just some generic advice and observations:
Disconnect your system from the Internet (if feasible).
If problem persists: Could it be an inside job?
Commands seem to be quasi-equidistant:
A (PID) controller running havoc or a (malevolent) script? Since external lights are also affected at the same time, I wouldn’t rule out a hack.
Thanks for your advice. No not an inside job. Im the only one out of my family that knows how to run it or control it 
The KNX IP/router doesnt have any open ports or port redirection to it, so I actually cant see how anyone could hack into the KNX Ip/router.
It must be openhab getting hacked or Alexa getting hacked?
no, I havent wolfgang, but I will. However, it has just this minute happened again, but I now think its the alexa app. It has picked up the CH temp set point as a thermostat in devices, which was set to 25 deg c. I dig log into the alexa app at around the same time logs. I have now deleted this thermostat on the Alexa App, and I will wait and see. .
Strange thing though, it ( alexa) never pick up the DHW temp adjust as a device on the app, and that keeps getting adjusted up to 75 degs.
Looks like it was the Alexa app, and the thermostat it had picked up. I deleted that device and its been good since!
Did you create some kind of Alexa routines? Just wondering why Alexa would change settings on her own?
Not in regard to the thermostat. I think Alexa found the ‘thermostat’ and made it a device, but it wasnt really configured on my KNX things as a thermostat, so it got confused. I do remember, asking alexa to turn the TV off one night, and Alexa sort off froze, didnt turn the TV off, then next thing I knew, the hot water temperature setting had increased 25 degs C.
Thanks for your help though!
I just wanted to check for you (and other readers), if there’s something to be aware of - as many of us have amazonechocontrol active with thermostats and others…
no problem.