3CX VPS, SBC in the office. Cisco SPA5xx units, seems that the BLFs for other extensions which are subscribed to appear to drop off.. they go into the error state. The registered extension itself is fine.. sends/receives calls via the SBC just fine. The BLFs do end up coming back. I started a tcpdump on the rPi SBC for capturing SIP traffic between it and one of the Cisco units. My guess is the SUBSCRIBE/NOFITY pair is missing some interval, causing the subscribed BLFs to time out or something. Anybody else behind and SBC with subbed BLFs with this behavior?