Successful login shows login form, wont let into the panel

[ashwalk33r]

Describe the issue

I login with valid credentials and after pressing login button I get back into https://admin.m2x.pl/login?from=%2Fserver%2FServer%25201

Proxied (cached) through CloudFlare https://www.cloudflare.com/

Sometimes it works, but no idea how to reproduce successful redirect to panel after successful login. I just have to keep repeating logging in and/or refreshing. It's supper annoying.

Exceptions & Other Logs

Requests/responses in order after pressing login:

Request URL: https://admin.example.com/auth/login
Request Method: POST
Status Code: 200 OK
Response: {"success":true}

Request URL: https://admin.example.com/v1/whoami
Request Method: GET
Status Code: 200 OK
{"authRequired":true,"loggedIn":false}

Request URL: https://admin.example.com/v1/serverIdentity?server=Server%201
Request Method: GET
Status Code: 200 OK
{
    "serverUUID": "xxxx-xxxx-xxxx-xxxx-xxxx",
    "serverName": "Server 1",
    "proxy": false
}

Plugin versions

PlanFabric-5.6-build-2883.jar

[ashwalk33r]

thanks for being a rubber duck - after writing it all here it came to me that this is Cloudflare caching issue, I've exempted caching from admin.example.com hostname and now login works fine