Connection issue with NPM and guacamole from some computers

[pinpoint90]

Ive setup guacamole as a proxy on NPM with ssl. It works on most private remote connections (i.e. my friends or parents house, or through cellular network), however I cant access when I use a remote computer connected to a corporate pc that is behind its own proxy.

When trying to access my guacamole server on my own domain, instead of login screen I get this error page:
"An error has occurred and this action cannot be completed. If the problem persists, please notify your system administrator or check your system logs."
It is worth to mention that rarely, once a day, I manage to get to the login screen after hours of randomly refreshing the page.

I can`t figure if the problem is in NPM or guacamole, but I suspect the problem to be a proxy/routing issue. Ive tried turning on/off all ssl settings http/2, HSTS, as well as common exploits and websockets.
Anyone know what might be the problem?

[pinpoint90]

I notice that there seem to be a 24 hour timeout where I am not able to access guacamole. When refreshing the webpage or disconnecting from guacamole, it takes 24 hours before I can connect to it again.
Maybe it is a NPM cache issue, I dont know. I am running NPM as a lxc container on a separate computer with proxmox.
I did not have this problem when running guacamole on docker on Synology NAS and using the internal reverse proxy on the nas. I belive synology uses nginx? Therefore I suspect that the problem is my NPM configuration...
Worth to mention that I also run my own domain through cloudflare (tested both with DNS proxy on and off).