Upload link problem

Hi, I used to create an upload link to a library, so people without authentication can send files for me.
Even huge files.
The upload works like a charm with Palemoon/Firefox, but not with Explorer, Edge or Google chrome.
Explorer, Chrome report unknown problem.
Edge just seems to freeze, then reports the webpage is not responding, and reloads the upload page.
Interesting is that everything works with small files, even with the “nasty” browsers".
Anyone had similar problem?
What could I do to solve this?
(Server version 6.2.5)
Thanks in advance

Could you post your your seahub.log?

Do you use a webserver like nginx?