diff --git a/offline/packages/calovtxreco/CaloVtxAlgoCNN.cc b/offline/packages/calovtxreco/CaloVtxAlgoCNN.cc
index df1a18f54d..e95ab5314f 100644
--- a/offline/packages/calovtxreco/CaloVtxAlgoCNN.cc
+++ b/offline/packages/calovtxreco/CaloVtxAlgoCNN.cc
@@ -27,7 +27,7 @@ namespace
   const std::string GeomNodeIhc = "TOWERGEOM_HCALIN";
 }  // namespace
 
-// onnxruntime session (pImpl, keeps Ort types out of the header)
+// onnxruntime session (pImpl)
 struct CaloVtxAlgoCNN::OnnxSession
 {
   Ort::Env env{ORT_LOGGING_LEVEL_WARNING, "CaloVtxAlgoCNN"};
@@ -44,6 +44,7 @@ struct CaloVtxAlgoCNN::OnnxSession
   }
 };
 
+CaloVtxAlgoCNN::CaloVtxAlgoCNN() = default;
 CaloVtxAlgoCNN::~CaloVtxAlgoCNN() = default;
 
 int CaloVtxAlgoCNN::Init(PHCompositeNode * /*topNode*/)
diff --git a/offline/packages/calovtxreco/CaloVtxAlgoCNN.h b/offline/packages/calovtxreco/CaloVtxAlgoCNN.h
index c1770de5b3..64b0dc2f8e 100644
--- a/offline/packages/calovtxreco/CaloVtxAlgoCNN.h
+++ b/offline/packages/calovtxreco/CaloVtxAlgoCNN.h
@@ -25,8 +25,8 @@ class CaloVtxAlgoCNN : public CaloVtxAlgo
     kOHC = 2
   };
 
-  explicit CaloVtxAlgoCNN() = default;
-  ~CaloVtxAlgoCNN() override; 
+  CaloVtxAlgoCNN();            // defined in the .cc, where OnnxSession is complete
+  ~CaloVtxAlgoCNN() override;  // (required for the unique_ptr pImpl member)
 
   int Init(PHCompositeNode *topNode) override;
   int CalculateVertex(PHCompositeNode *topNode, float &zvtx) override;
diff --git a/offline/packages/calovtxreco/CaloVtxAlgoMLP.cc b/offline/packages/calovtxreco/CaloVtxAlgoMLP.cc
index a2199193da..de41927abf 100644
--- a/offline/packages/calovtxreco/CaloVtxAlgoMLP.cc
+++ b/offline/packages/calovtxreco/CaloVtxAlgoMLP.cc
@@ -13,6 +13,7 @@
 #include <phool/getClass.h>
 
 #include <array>
+#include <limits>
 
 int CaloVtxAlgoMLP::Init(PHCompositeNode *topNode)
 {
@@ -49,6 +50,8 @@ int CaloVtxAlgoMLP::Init(PHCompositeNode *topNode)
 
 int CaloVtxAlgoMLP::CalculateVertex(PHCompositeNode *topNode, float &zvtx)
 {
+  zvtx = std::numeric_limits<float>::quiet_NaN();
+
   TowerInfoContainer *emcalre_towers = findNode::getClass<TowerInfoContainer>(topNode, "TOWERINFO_CALIB_CEMC_RETOWER");
   TowerInfoContainer *hcalin_towers = findNode::getClass<TowerInfoContainer>(topNode, "TOWERINFO_CALIB_HCALIN");
   TowerInfoContainer *hcalout_towers = findNode::getClass<TowerInfoContainer>(topNode, "TOWERINFO_CALIB_HCALOUT");
@@ -304,6 +307,11 @@ int CaloVtxAlgoMLP::CalculateVertex(PHCompositeNode *topNode, float &zvtx)
 
     }
 
+  if (ijet < 2)
+    {
+      return Fun4AllReturnCodes::EVENT_OK;
+    }
+
   // TODO: fill `features` from topNode in the exact order documented in
   // VertexMLP.h (emcal/ohcal lead+sublead flags, zmean/zsig/zskew,
   // energy, exj). This is the same per-event extraction CaloVtxReco used