Also something else, rather strange with your site. The wp-rocket cache signature <!-- This website is like a Rocket, isn't it? should appear at th...

log files, .ht*** files and other files should be automatically blocked (403) not by you but from the hosting setup. Unless you manage your server, th...

Wouldn't that totally make mentions useless ?

It is the same error as here: and also a LOT of same problem if you search the internet. Related either to hosting (tmp path) or a plugin. Try to dis...

Can you make the wp-config.php 644 and see if the error is gone ? And try things ONE BY ONE. Not all at once. No need to delete Rocket cache, just dis...

Also, i found your error (not exactly but most of it) in Wordpress.org, in two different caching plugins forums. I see you run Rocket cache ? Could yo...

@tgw Can you see/check what is the FILE permission of wp-config.php ? Is it 644 or 600 ?

And your problems started not as you say recently but in JUNE (or at June DEBUG was enabled) : [24-Jun-2019 12:12:05 UTC] PHP Warning: session_start()...

@tgw I was able to download your huge debug.log of your site and that is something it SHOUDN'T happen. It should return a 403 on a properly set web se...

Ok, i see that you are on a Windows IIS server. Sorry i have no idea about Microsoft IIS. (still you should remove the "index.php" from your permalink...

Also this: http: // www . zzzzzzz . nl/index.php/community/ is WRONG (everywhere in your wordpress urls). Fix it. In permalinks of WP.

Ok, this seems like a "captcha" related problem. A long shot, still do you know if you are on a LiteSpeed web server ?

and the problem appeared all of a sudden ? It was working right, nothing at all changed and it appeared ?

I have seen that once and came from some added "hooks" in my theme. If it doesn't come from your plugins, maybe it comes from your theme ? Or any cust...

I can't help on this, but i have seen that twice myself in my tiny forum. Not sure if 1.64 was installed or the previous version when it happened. But...