Cannot upload files from local network

Hi,

I’ve owncloud (10.5.0) installed on my ubuntu server (18.04, php7.4) and I’m running into a problem.
I can not upload files larger than a few MB’s to owncloud from a device in my local network. Not via the windows app or webbrowser, in the browser it gives a file upload timeout error. . If I switch to a other network or use a vpn uploading works just fine.

Please advice how to fix this.

Expected behaviour

Files should be uploading

Actual behaviour

I get an timeout error.

Server configuration

Operating system:
Ubuntu server 18.04
Web server:
Apache2
Database:
Mysql
PHP version:
7.4
ownCloud version: (see ownCloud admin page)
10.5.0
Updated from an older ownCloud or fresh install:
updated
Where did you install ownCloud from:
?
Signing status (ownCloud 9.0 and above):

Login as admin user into your ownCloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results into https://gist.github.com/ and puth the link here.

The content of config/config.php:

Are you using external storage, if yes which one: local/smb/sftp/…

Are you using encryption: yes/no
no
Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/…
no

Hey,

this sounds to me like a network issue and looks similar to: