I've done a first fix and I need your help for testing. The fix is in the authorization server files and so no new release is needed.
The fix should solve the problem with own apps. I'm not sure if it fixes alo the problem with the error when a channel is saved (My problem is that I can't reproduce this problem on my own test server).
You must do a new authorization for the Facebook account and copy/paste the displayed (new) token into the field in the dialog.
If you use your own app, you must enter the app data and activate the own app BEFORE you press the authorization button. The token for your own app is different from the token for the standard app!