Reverse proxy diagnostics

NethServer Version: NethServer release 7.9.2009 (final)
Module: Web Server 3.12.2

Im running erpnext instances on the lan and accessing from internet via nethservers reverse proxy - this operates OK but access is intermitantly blocked. Ive assessed this is the reverse proxy because i can access the instance via the LAN whilst it is blocked. Any advice regarding specific tools/methods to diagnose/fix the issue appreciated please