That looks like the Apache access log, not the PHP errors log.
Anyway, permissions problems are worth investigating. You need to look (and set) ownerships also - Linux permissions (like 755 etc) don’t mean anything without the associated ownership.
This, in turn, needs to be confronted with the user name that is trying to access the file (in this case, which user name your web server process is running under).
Well I have given up with Siteground. They are automatically changing file permissions in the background for some peculiar reason. I have moved away to Krystal.co.uk for much cheaper hosting and set up a suitecrm system there. It works! No issues yet. I have transferred my customisations across and moved the database as well. All fine.