Since this topic got marked as solved, I opened a new one. 

cant edit text block on the side column. no problem on the main page.

I changed to the default theme, didn't work. not even changing the language back to default:

 

 

 

I will need to move this to a ticket as there seems to be a conflict happening in Javascript that will need to be investigated here. Someone will look at this as soon as they can.

This is caused by a widget which contains broken/invalid HTML code.