This is what I do think is the problem. Note how it recognizes 192.168.255.15. Then if we remember this line:
That indicates it should really use 192.168.255.151. It doesn’t recognize that 192.168.255.15 is a valid reverse proxy. That means it detects the remote IP incorrectly.
Can you try adding this to /etc/foreman/settings.yaml:
---
# ... existing config
:trusted_proxies:
- "127.0.0.0/8"
- "::1"
- "192.168.255.15"
Then run systemctl restart foreman and try again.