A request-response for the "WCF-Custom" adapter at receive location "sap://CLIENT=xxx;LANG=DE;@d/ABCDEF?ListenerDest=VWXYZ&RfcSdkTrace=True&AbapDebug=False" has timed out before a response could be delivered.
...then your Receive Location with a WCF-Custom adapter and SAP-Binding run into a time-out while sending the reply to the SAP system. In this case, you might accidently have used a transactional RFC connection, that happens if you use a Request Response Receive Location instead of a One-Way Receive Location (for example, because Visual Studio created you a binding with Request Response RL).
To solive this, you could either use a Request Response RL and send the response by your own, or you simply switch to a One-Way RL.
