Intermittent xfreerdp hang only through VPN

[Younes Manton]

Hi,

I've had this problem for at least a couple of years. Whenever I
connect to a Windows machine via xfreerdp over my work place VPN the
xfreerdp client inevitably hangs. Occassionally SSH sessions will also
hang, but this happens much less often. I never see either problem
when not connected over VPN.

I normally run OpenConnect via Network Manager, but I recently ran it
on the command line with -v to watch the output. As best as I can tell
the hangs always follow a CSTP rekey and the only thing that's
different from the usual is that these lines begin to appear:

Send CSTP Keepalive
Send CSTP DPD
Got CSTP DPD response

They seem to stop being emitted once I kill the unresponsive xfreerdp client.

On the Windows side I see the following in the Event Viewer every time
xfreerdp hangs:

The Terminal Server security layer detected an error in the protocol
stream and has disconnected the client. Client IP: <my IP>.

Anything I can do to debug this?