Nginx access.log

"GET /iredadmin/activities/quarantined/raw/JhsqVyjDOwzf HTTP/1.1" 504 578 "https://xxxxx.xx/iredadmin/activities/quarantined" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.110 Safari/537.36"

/var/log/messages

Dec 19 12:05:48 mail uwsgi: mail.xxx.xxx [pid: 704|app: 1|req: 12/21] xx.xxx.xxx () {52 vars in 850 bytes} [Wed Dec 19 12:05:48 2018] GET /iredadmin/login => generated 5029 bytes in 234 msecs (HTTP/1.1 200) 2 headers in 146 bytes (2 switches on core 0)
Dec 19 12:05:50 mail uwsgi: mail.xxx.xxx [pid: 703|app: 1|req: 3/22] xx.xxx.xxx () {64 vars in 1158 bytes} [Wed Dec 19 12:05:50 2018] POST /iredadmin/login => generate 0 bytes in 14 msecs (HTTP/1.1 303) 3 headers in 214 bytes (2 switches on core 0)
Dec 19 12:05:51 mail uwsgi: mail.xxx.xxxh [pid: 704|app: 1|req: 13/23] xx.xxx.xxx () {58 vars in 1034 bytes} [Wed Dec 19 12:05:50 2018] GET /iredadmin/dashboard/checknew => generated 23804 bytes in 1478 msecs (HTTP/1.1 200) 2 headers in 146 bytes (2 switches on core 0)
Dec 19 12:06:07 mail uwsgi: mail.xxx.xxx [pid: 704|app: 1|req: 14/24] xx.xxx.xxx () {56 vars in 1024 bytes} [Wed Dec 19 12:06:05 2018] GET /iredadmin/activities/quarantined => generated 26507 bytes in 1180 msecs (HTTP/1.1 200) 2 headers in 146 bytes (2 switches on core 0)

What's worse, is now iredadmin become unresponsive. Reboot required.

==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 0.9.9
- Deployed with iRedMail Easy or the downloadable installer? Download
- Linux/BSD distribution name and version: Centos 7.6
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? Pro 3.0
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

   Hello,

we have the same problem after upgrade. If I restart iredadmin, then I can connect to iRedAdmin-Pro, browse though
menu, but not "View or hide mail body and headers". If second admin connect to iRedAdmin-Pro, then we are getting error.:

504 Gateway Time-out

2018/12/19 10:59:31 [error] 16981#0: *1561 upstream timed out (110: Connection timed out) while reading response header from upstream, client: x.x.x.1, server: _, request: "GET /iredadmin/activities/quarantined/raw/eW90FWB6k7Ep HTTP/1.1", upstream: "uwsgi://127.0.0.1:7791", host: "x.x.x", referrer: "https://x.x.x/iredadmin/activities/quarantined"
2018/12/19 11:00:45 [error] 16981#0: *1561 upstream timed out (110: Connection timed out) while reading response header from upstream, client: x.x.x.1, server: _, request: "GET /iredadmin/dashboard HTTP/1.1", upstream: "uwsgi://127.0.0.1:7791", host: "x.x.x", referrer: "https://x.x.x/iredadmin/activities/quarantined"
2018/12/19 11:00:48 [error] 16980#0: *1612 upstream timed out (110: Connection timed out) while reading response header from upstream, client: x.x.x.4, server: _, request: "GET /iredadmin/dashboard HTTP/1.1", upstream: "uwsgi://127.0.0.1:7791", host: "x.x.x"
2018/12/19 11:05:51 [error] 16980#0: *1640 open() "/var/www/html/iredmail/dashboard" failed (2: No such file or directory), client: x.x.x.4, server: _, request: "GET /iredmail/dashboard HTTP/1.1", host: "x.x.x"
2018/12/19 11:31:12 [error] 16980#0: *1782 upstream timed out (110: Connection timed out) while reading response header from upstream, client: x.x.x.4, server: _, request: "GET /iredadmin/activities/quarantined/raw/kCPn5Yz6fQgE HTTP/1.1", upstream: "uwsgi://127.0.0.1:7791", host: "x.x.x", referrer: "https://x.x.x/iredadmin/activities/quar … g=RELEASED"
2018/12/19 11:31:22 [error] 16980#0: *1790 upstream timed out (110: Connection timed out) while reading response header from upstream, client: x.x.x.4, server: _, request: "GET /iredadmin/activities/quarantined/raw/0RUVEDxbu6xX HTTP/1.1", upstream: "uwsgi://127.0.0.1:7791", host: "x.x.x", referrer: "https://x.x.x/iredadmin/activities/quar … g=RELEASED"
2018/12/19 14:11:43 [error] 16980#0: *2486 upstream timed out (110: Connection timed out) while reading response header from upstream, client: x.x.x.1, server: _, request: "GET /iredadmin/dashboard HTTP/1.1", upstream: "uwsgi://127.0.0.1:7791", host: "x.x.x", referrer: "https://x.x.x/iredadmin/dashboard"

Could you try this:
Open file /opt/www/iredadmin/rc_scripts/uwsgi/rhel.ini, append line below to the file:

threads = 20

Then restart iredadmin service.

Is "iredadmin" service still running when you get this "504 Gateway Time-out" error?

Patch for iRedAdmin-Pro-SQL-3.0 AND iRedAdmin-Pro-LDAP-3.2:
https://pastebin.com/raw/KVAuDm4k

if you're not familiar with patch, feel free to contact me (zhb _at_ iredmail _dot_ org) to get a patched version.

Yes, I can also confirm that this latest version is now working. Thanks.