@@ -635,6 +635,14 @@ def _filter_ttl(
             )
         ]
 
+        df_to_join = df_to_join.persist()
+    else:
+        df_to_join = df_to_join[
+            # do not drop entity rows if one of the sources returns NaNs
+            df_to_join[timestamp_field].isna()
+            | (df_to_join[timestamp_field] <= df_to_join[entity_df_event_timestamp_col])
+        ]
+
         df_to_join = df_to_join.persist()
 
     return df_to_join
Original file line number	Diff line number	Diff line change
`@@ -635,6 +635,14 @@ def _filter_ttl(`
`635`	`635`	`)`
`636`	`636`	`]`
`637`	`637`
	`638`	`+ df_to_join = df_to_join.persist()`
	`639`	`+ else:`
	`640`	`+ df_to_join = df_to_join[`
	`641`	`+ # do not drop entity rows if one of the sources returns NaNs`
	`642`	`+ df_to_join[timestamp_field].isna()`
	`643`	`+ \| (df_to_join[timestamp_field] <= df_to_join[entity_df_event_timestamp_col])`
	`644`	`+ ]`
	`645`	`+`
`638`	`646`	`df_to_join = df_to_join.persist()`
`639`	`647`
`640`	`648`	`return df_to_join`