Possible misconfiguration with the secondary input
Also related to https://github.com/dmwm/WMCore/issues/8983
and initially reported and discussed over this JIRA ticket: https://its.cern.ch/jira/browse/CMSCOMPPR-4523

I'm still debugging it, but I have strong suspicious on a badly configured pileup task. More news this afternoon.
diff --git a/src/python/WMCore/WMRuntime/Scripts/SetupCMSSWPset.py b/src/python/WMCore/WMRuntime/Scripts/SetupCMSSWPset.py
index 346c80eef..67a7c7b45 100755
--- a/src/python/WMCore/WMRuntime/Scripts/SetupCMSSWPset.py
+++ b/src/python/WMCore/WMRuntime/Scripts/SetupCMSSWPset.py
@@ -499,7 +499,7 @@ class SetupCMSSWPset(ScriptInterface):
         prodsAndFilters.update(self.process.producers)
         prodsAndFilters.update(self.process.filters)
         for key, value in prodsAndFilters.items():
-            if value.type_() in ["MixingModule", "DataMixingModule"]:
+            if value.type_() in ["MixingModule", "DataMixingModule", "PreMixingModule"]:
                 mixModules.append(value)
             if value.type_() == "DataMixingModule":
                 dataMixModules.append(value)
['src/python/WMCore/WMRuntime/Scripts/SetupCMSSWPset.py']