Whenever incoming request/response doesn't conforms to wsdl structure specified, we'll run into below error/exception,

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ERROR [bwEngThread:In-Memory Process Worker-3] com.tibco.bw.binding.soap - $$$$$ ERROR Occured while converting XiNode to Axiom
WARN  [bwEngThread:In-Memory Process Worker-3] com.tibco.bw.core - TIBCO-BW-CORE-400001: Exception while constructing CatchAllFaultDetails document java.lang.NullPointerException
++++++++++++++++++++++++
 

Check incoming request/response structure (soap envelop) and conform with wsdl,  if it's not inline then you need to check with your provider or client for necessary changes. If its inline then please check with TIBCO Support.