We seem to be seeing this type of issue randomly on two sites???
SessionHandler::read(): open(/tmp/sess_10dl8rd07eih11sch783j97tc4, O_RDWR) failed: Permission denied (13)
Checked permissions, there's no issue there, so what could be the issue?
Just as a follow up to let other know what fixed the issue for me.
Basically, it was a space issue as previously mention by Mnkras, so thank you for giving me a good starting point :)
I had to create a new tmp file at the root of the hosting package and then create a php.ini file and set the save session path to this directory.