fix

beacon-chain/rpc/eth/beacon/handlers_pool.go

@@ -197,7 +197,16 @@ func (s *Server) SubmitAttestations(w http.ResponseWriter, r *http.Request) {
 
 	var sourceAttestations []*structs.Attestation
 	if err := json.Unmarshal(req.Data, &sourceAttestations); err != nil {
-		httputil.HandleError(w, fmt.Sprintf("Failed to unmarshal request: %v", err), http.StatusInternalServerError)
+		var singleAttestation *structs.Attestation
+		if err := json.Unmarshal(req.Data, &singleAttestation); err != nil {
+			httputil.HandleError(w, "Could not parse data into attestations: "+err.Error(), http.StatusBadRequest)
+			return
+		}
+		sourceAttestations = append(sourceAttestations, singleAttestation)
+	}
+
+	if len(sourceAttestations) == 0 {
+		httputil.HandleError(w, "No data submitted", http.StatusBadRequest)
 		return
 	}