My Tinymce is not showing up by default.

All out of the sudden, without any new plugin installation or what so ever, VC plugin started to force my text editor (when creating a new entry) to switch from TinyMCE to HTML. I have tested:

* Switch themes with Visual Composer plugin activated – the problem remains. I have the Visual Composer plugin installed in wordpress, but I have no purchase code since it came with my theme. Therefore I cannot ask for help at the VC page. 
* Deactivate the VC plugin – The problem disappears
* Add the add_filter function on my functions.php – website gets broken
* When I open my browser console and type `getUserSetting(\'editor\')`, I recieve the answer “html”. If I type in s`etUserSetting(\'editor\', \'tinymce\')`, I get the answer “editor”. The I type `getUserSetting(\'editor\')` to see if anything has changed and I get the answer “tinymce”. But then when I refresh, the bug is still back on.

I have read this but I don\'t know where to apply the provided solution and since I have a very recent account here I can\'t comment and ask. Perhaps that will solve my issue, but where do I apply the provided solution?

I have also read about this possible solution which sounds very plausible since this issue did not come from any new plugin install or other change in the system, but How do I do it? How do I delete a cookie from the database in this case?

Any other way how can I solve this? I would be really appreciated for any help or guidance since I am stuck for days in this issue...