502 and 504 error shows up only on specific clients

Hello @all

I'm facing a strange problem using nginx as a reverse proxy in my setup.
I have setup several subdomains leading to different internal webservers (so far all ok)

On my PC the connection works to all the proxied servers using

- FireFox
- Edge Browser

but when I access the same subdomains from my Chrome Browser I always get a 502 Bad Gateway or 504 Gateway Time Out

Same problem on my Android phone using Chrome...

On another PC in the same network it works in Edge, Firefox and Chrome
On a 3rd PC outside the local network it works as well using Edge, Firefox and Chrome

I have already tried to disable all installed Chrome extensions and additionally to call the URLs in private mode without success.
I always get the timeouts

I had a look at the log files but got no meaningful hint or cause of this timeout - at least for me :-)


So here's the error log of one subdomain from a local nextcloud setup which leads to the 504 Error:


https://pastebin.com/hkCvXjMa

Any help is very much appreciated.

Best regards
Bastian