Some routers reject requests in succession too fast

Some requets in succession fail with error code 5.

Debug log:
$ upnp-router-control -i eth0 --debug
* Initializing GUI...
* Showing GUI...
* Starting UPnP Resource discovery... done
==> Device Available: Netgear DG834PN Router
  Model description: Netgear DG834PN Router
         Model name: ADSL Firewall Router
       Model number: DG834PN
              Brand: Netgear
   Presentation URL: http://192.168.7.1/
                UPC: (null)
 Unique Device Name: uuid:824ff22b-8c7d-41c5-a131-44f534e12555
   Enum services...
     Service: urn:upnp-org:serviceId:OSInfo
        Type: urn:schemas-microsoft-com:service:OSInfo:1
   Enum sub-devices...
     Sub-Device: WANDevice
       Enum services...
         Service: urn:upnp-org:serviceId:WANCommonInterfaceConfig
            Type: urn:schemas-upnp-org:service:WANCommonInterfaceConfig:1
> GetCommonLinkProperties
> GetTotalBytesSent
> GetTotalBytesReceived
> GetTotalPacketsSent
> GetTotalPacketsReceived
[EE] GetTotalBytesSent: Connection terminated unexpectedly (5)
       Enum sub-devices...
         Sub-Device: WANConnectionDevice
           Enum services...
             Service: urn:upnp-org:serviceId:WANIPConnection
                Type: urn:schemas-upnp-org:service:WANIPConnection:1
> SetConnectionType
> GetConnectionTypeInfo
> GetStatusInfo
> GetNATRSIPStatus
> GetGenericPortMappingEntry
> GetSpecificPortMappingEntry
> AddPortMapping
> DeletePortMapping
> GetExternalIPAddress
             ** Subscribed to WANIPConnection events
Request for external IP address... successful [92.27.121.31]
Request for connection status info... failed
[EE] GetStatusInfo: Connection terminated unexpectedly (5)
Request for NAT and RSIP availability... successful [RSIP=no, NAT=yes]
Event: Connection status: Connected
Event: External IP: 0.0.0.0
Request for external IP address... successful [92.27.121.31]
Event: Ports mapped: 1
==> List port mapped (1)
[EE] GetGenericPortMappingEntry: Connection terminated unexpectedly (5)
GetTotalBytesReceived() duration: 1.011610s
[EE] GetTotalBytesSent: Connection terminated unexpectedly (5)
GetTotalBytesReceived() duration: 1.014549s
GetTotalBytesSent() duration: 1.013581s
GetTotalBytesReceived() duration: 1.012564s
[EE] GetTotalBytesSent: Connection terminated unexpectedly (5)
GetTotalBytesReceived() duration: 1.014011s
[EE] GetTotalBytesSent: Connection terminated unexpectedly (5)
GetTotalBytesReceived() duration: 1.013165s

Affected routers:
* Netgear DG834PN
* 3Com ADSL 11g Router (unknown model, maybe "3Com® OfficeConnect® ADSL Wireless 11g Firewall Router")