Sysadmin 503 error please advise

Hello
I have one of my resources on a webpage dosn't load

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Code (Text):

[LIST]
[LIST]
[*][B]Request URL:[/B]https://domain.com/courses/coursename/lessons/welcome/?content-item-only=yes
[*][B]Request Method:[/B]GET
[*][B]Status Code:[/B]503 
[*][B]Remote Address:[/B]1.1.1.1:443
[*][B]Referrer Policy:[/B]no-referrer-when-downgrade
[/LIST]
[*][B]Response Headers[/B]
[LIST]
[*][B]content-length:[/B]0
[*][B]date:[/B]Fri, 09 Jun 2017 23:43:05 GMT
[*][B]server:[/B]nginx
[*][B]status:[/B]503
[*][B]x-content-type-options:[/B]nosniff
[*][B]x-varnish:[/B]5
[*][B]x-xss-protection:[/B]1; mode=block
[/LIST]
[*][B]Request Headers[/B]
[LIST]
[*][B]:authority:[/B]domain.com
[*][B]:method:[/B]GET
[*][B]:path:[/B]/courses/coursename/lessons/welcome/?content-item-only=yes
[*][B]:scheme:[/B]https
[*][B]accept:[/B]text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
[*][B]accept-encoding:[/B]gzip, deflate, br
[*][B]accept-language:[/B]en-US,en;q=0.8,ar;q=0.6
[*][B]cookie:[/B]_ym_uid=149709851618ws331606615; _ym_isad=2; _ym_visorc_4352009644=w; __stripe_mid=b1e4wsd043-f681-48cd-baae-769f425fce44; __stripe_sid=fcd5w2d72c-3851-483a-8b54-afd9093ew8a8dadf
[*][B]referer:[/B]https://domain.com/courses/coursename/lessons/welcome/
[*][B]upgrade-insecure-requests:[/B]1
[*][B]user-agent:[/B]Mozilla/5.0 (Linux; Android 6.0; Nexus 5 Build/MRA58N) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.86 Mobile Safari/537.36
[/LIST]
[*][B]Query String Parameters[/B]view source
view URL encoded
[LIST]
[*][B]content-item-only:[/B]yes
[/LIST]
[/LIST]

please advise where to dig?

 

sometimes also it gives me error 500 for that specifc request, otherewise the whole website is just fine

 

I was able to isolate the problem and it ONLY happens when the WordPress theme updates to the newest version, interestingly even if I pick another theme (e.g twenty seven) the problem persists [but this time is with loops while loading this specific page], the theme company claims that it is a server issue? I went thru the Nginx wp-secure and disabled it altogether, still there? any ideas?

 

no, it only happens with that specific theme update

 

one of the new thing added in the updated theme version is comments (to the lesson page that have the troubles), I'm using Facebook comments plugin, does this have anything to do with that?

 

it is not the maintenance as it only happens on a specific ajax loaded page,

thanks for the tip though

I tried one more time and the twenty-fifteen theme fixed the problem, that means it is in the theme update, what is the best practice for a company with poor themes like this, shall i make staging server to test before updating, shall I disable the auto-update for the theme only???

 

This looks like an interesting tool

https://support.pagely.com/hc/en-us/articles/203115924-Cloning-Sites-with-Pagely-Sync

 

or this one, but need to play with it a little for centimod

https://github.com/blindpet/wpbullet-autostaging-scripts/blob/master/nginx-staging.sh