Errors when installing CMS Builder

Hi,
I am seeing an error when trying to install CMSB:
Warning: session_start(): open(/tmp/sess_780464de0539451a806538a189e9f74c, O_RDWR) failed: Permission denied (13) in /home/muscle/public_html/cms/lib/init.php on line 620 Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/muscle/public_html/cms/lib/init.php:620) in /home/muscle/public_html/cms/lib/init.php on line 620 Warning: Cannot modify header information - headers already sent by (output started at /home/muscle/public_html/cms/lib/init.php:620) in /home/muscle/public_html/cms/lib/menus/header.php on line 4

I spoke to my web hosting support who deleted all the files from /tmp yesterday which got rid of the error. I tried to visit the page again today and the error is back.

Here's what my web hosting support had to say:
From what I am seeing it is a coding error that is causing this, information is being sent before the start of the session and due to this the code is failing to execute. I can delete the temporary file for you again, but you may want to check with CMS builder's support if it continues to occur.
Something in the code is generating a temporary session file, and it is being called to at the start of the session for what you are trying to complete, according to the error it appears that it is cms/lib/init.php that has made the file and then tries to make it again when the session_start() function in that site is called, so this causes a conflict.

I would like to resolve this issue incase it causes more problems in the future. I am now concerned that it could be causing the below caching issue on the same server:

https://www.interactivetools.com/forum/forum-posts.php?Caching-issue-on-site---users-can-t-logoff-80749

Thanks for your help!