TV: 42PFL6057H/12 using HD-recorder as tuner. Latest software: 133

This nice TV is installed in my dad’s home. He, as a person of 90 years, he just want to watch TV and switching channels and switch it on and off.
I have now installed Skype, login name and password and activated “automatic log in at start up”
To test all this I made a video call and worked. If he gets an incoming call, he can press OK to accept the call, and make a conversation.
But now my question: how can he terminate the call by pressing one button and come back into the program what he was watching?
I could not terminate the call (on his TV while a friend was making a Skype conversation) like it should be. Just by switching the TV off, and on again could bring a “not acceptable solution” But I discovered that the login-data off Skype were gone, no name and password, and the “automatic log in at start up” was activated!
I have tried different times to log in, and in some cases I had strange effects: sometimes the TV started up with sound and no image (I mean television, no Skype). The only way out was a total reset: unplug the power for 30 sec. and restart.
Is there anyone who can tell me what I am doing wrong?
Thanks.
Julien