Nextcloud behind Apache Traffic server

I have an issue with nextcloud which lives behind apache traffic server. Everything works (kindof), so you can connect to the web interface and connect clients. Uploads work and you can see everything working ok until you try to delete something. Then you get an error and the file is not removed from the server. File permissions and everything is fine as if I connect directly (inside LAN) directly to IP everything works?
Any ideas??

PS: Behind classic Apache with reverse proxy I had no issues.