Page Builder editor is removing some html

Hello I am adding some customized source code in Text block in the page builder .. but after saving it, if I come to edit the source again I find the editor have cleaned some elements attribute ..
for example I was adding  id attribute to <ul> .. when I save it for the first time it is saved correctly .. but If I want to edit the source again I find it gone

P.S. Im using the old version of the theme : 3.5