HA intermittently hangs on "Loading Data..."

Hey,

I have NGINX 3.5.0 reverse proxy running with HA.
NGINX listens on TCP443 for HTTPS, and TCP8081 for HTTP

HA listens on TCP80 for HTTP (so I can access from LAN without SSL if I ever need too) with configuration.yaml having:

http:
  server_port: 80
  use_x_forwarded_for: true
  trusted_proxies:
    - 172.30.33.0/24
    - 192.168.222.0/24
    - 172.16.221.0/24
    - 127.0.0.1

My firewall NATs TCP443 inbound to NGINX reverse proxy on TCP443 (I use Alexa so need it open)
Also a NAT for TCP80 inbound to NGINX on TCP8081 for cert renewals (manually enable policy when renewing cert)

I have split DNS for ‘ha.mydomain.com’ to resolve public IP of firewall via Internet, or local IP of HA if on LAN. So basically going to https://ha.mydomain.com/ generally works from Internet and LAN just fine.

However intermittently (seems to happen daily now) when launching HA from a browser it just sits there showing “Loading data…” when using HTTPS from my LAN. However the iPhone app works fine locally though (also set to use HTTPS). HTTP also works fine locally. Seems to point to NGINX but I can’t work out why. I’ve tried clearing cache, different browsers etc, all do the same.

Powering HA off and back on sorts it for a little while, but then the next day it just goes back to “loading data…” again, retries indefinitely, never succeeds

(I know I could just stick to HTTP internally but prefer HTTPS for both, as chrome likes to try and redirect HTTP to HTTPS automatically, and don’t want to turn that setting off or have to run incognito mode every time)

Any ideas?