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Sorry to hear you’re facing problems 
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In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 20.0.5): 27.0.2
Operating system and version (eg, Ubuntu 20.04): Debian 12
Apache or nginx version (eg, Apache 2.4.25): replace me
PHP version (eg, 7.4): 8.1
The issue you are facing:
I am running Nextcloud as a VM on ESXi 8. I am using Nginx Proxy Manager as a reversed proxy.
My DNS is handled by Cloudflare, proxy on/off doesn’t make a difference.
The problem is internally when i upload a couple of GB’s the transfer speed goes up to about 60MB/s and then drops to 4/5 MB’s. PfSense shows me this.
I use to have Nextcloud on an own external IPv4 address, i didn’t have this problem with that setup.
From a different external location i am getting about 25MB/s. Still not great but better than 5MB/s. So the problems seems to be internally. I am not using split DNS but PfSense does do Hairpin as far as i know.
Any ideas on how to fix this? I think the problem isn’t NC but NPM/CF. Since i didn’t have these problems before.
Is this the first time you’ve seen this error? (Y/N):
Steps to replicate it:
The output of your Nextcloud log in Admin > Logging:
PASTE HERE
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
PASTE HERE
The output of your Apache/nginx/system log in /var/log/____:
PASTE HERE
PASTE HERE
Output errors in nextcloud.log in /var/www/ or as admin user in top right menu, filtering for errors. Use a pastebin service if necessary.
PASTE HERE