Hello Fernando,
Thank you for your quick reaction. I am quite sure something in the plugin is conflicting with the Moodle code.
I have removed the fn_marrking folder in blocks/ and then cleared the cache and the textbox aligned cirrectly. I have put back the fn_marking folder, cleared the cache and the textbox jumps to the left. removed the folder again, cleared the cache and the textbox ligned out correctly. put the folder back, cleared the cache, textbox jumps to the left. I have repeated these steps 3 times over and over again
If you are willing to test it on your site I will be grateful. I am unfortunately not a programmer, so this code is abracadabra for me :$