504 error with Chrome, Edge, Opera No error with Firefox, Brave or app

[Philmo67]

Hello,
I have a confusing problem: redirects to my services only work when using Firefox, or the dedicated Android apps (in LAN, WLAN and WAN, so the network/firewall configuration can be considered correct). I can't connect with Chrome or Edge, I get a 504 error.
I've purged the caches, including HSTS.
The services are set up as follows:

{
  "id": 1,
  "created_on": "2021-08-23 23:48:41",
  "modified_on": "2021-11-29 12:24:09",
  "owner_user_id": 1,
  "domain_names": [
    "service.domain.org"
  ],
  "forward_host": "192.168.1.20",
  "forward_port": 80,
  "access_list_id": 0,
  "certificate_id": 19,
  "ssl_forced": true,
  "caching_enabled": false,
  "block_exploits": true,
  "advanced_config": "",
  "meta": {
    "letsencrypt_agree": false,
    "dns_challenge": false
  },
  "allow_websocket_upgrade": true,
  "http2_support": false,
  "forward_scheme": "http",
  "enabled": 1,
  "locations": [],
  "hsts_enabled": false,
  "hsts_subdomains": false
}

Error log shows :
2021/12/07 21:40:31 [error] 13228#13228: *114081 upstream prematurely closed connection while reading response header from upstream, client: 192.168.1.2, server: service.domain.org, request: "GET / HTTP/2.0", upstream: "http://192.168.1.20:80/", host: "service.domain.org"

Access log shows :
[07/Dec/2021:21:39:40 +0000] - - 499 - GET https service.domain.org "/" [Client 192.168.1.2] [Length 0] [Gzip -] [Sent-to 192.168.1.20] "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.55 Safari/537.36 Edg/96.0.1054.43" "-" [07/Dec/2021:21:40:31 +0000] - 502 502 - GET https service.domain.org "/" [Client 192.168.1.2] [Length 556] [Gzip -] [Sent-to 192.168.1.20] "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.55 Safari/537.36 Edg/96.0.1054.43" "-" [07/Dec/2021:21:41:23 +0000] - 502 502 - GET https service.domain.org "/favicon.ico" [Client 192.168.1.2] [Length 556] [Gzip -] [Sent-to 192.168.1.20] "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.55 Safari/537.36 Edg/96.0.1054.43" "https://service.domain.org/"

Where to start investigating?

[Philmo67]

I tested using Brave and services work fine, however, no success using Opera.
So the same services are OK using Firefox and Brave but sending a 504 error using Chrome, Edge and Opera ...