Draytek 2925, running latest firmware (3.8.9.8)

I needed a 9GB file from a mate, so I quickly opened a port redirection (wan:2222 to local:22) under NAT | Port Redirection

Mate is able to sftp a file over no issues there. However I notice that the main Data Flow Monitor page for isn't showing/logging traffic on the redirected port number, but other traffic for this LAN IP on non-redirected ports is reported fine. Looking at just the single machine (by clicking on its IP address) show a graph, but again it is missing the incoming sftp transfer.

Code:

RX Rate(Kbps): 12

Oddly, the RX total at the bottom appears to be correct

Code:

Current / Peak / Speed: 19487 / 58976 / Auto

However, if I look at the traffic graph (Diagnostics | Traffic Graph), I can see the RX is at this level is correctly reporting the incoming data. Likewise Online Status | Physical Connection is happily reporting:

Code:

RX Rate(Mbps): 19.43

I had a 2925 and now have a 2926. The data flow monitor page sometimes shows data flowing and other times it is completely blank (by which I mean there is nothing in any of the columns), for no reason that I have been able to discern.