PRO-Sites and Visual Composer

Hi Guys,

our issue is as follows.

1. We developed a site for a client as paid prosite level.

2. Most of the site was created With Visual Composer by us as master admin

3. All of client users are assigned as administrators to their own site.

4. we put many Elements of the pages in a VC text block element as it is really easy to review and edit

5. when us as master admin make any change all is ok

6. when my client is making changes it strips the HTML from the text block element.

7. We had a lengthy support with WPBakery and they say the following:
"We do not have a setting or filter in visual composer to give same rights as admin to other user role as roles are managed by WordPress core. It might be something that WPMU user account uses that strips the code. "

Can you please help us figure out why this is happening?