diff --git a/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/agenda/operation/AbstractChangePlanItemInstanceStateOperation.java b/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/agenda/operation/AbstractChangePlanItemInstanceStateOperation.java
index 501ee43e9b5..2616ea28d2b 100644
--- a/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/agenda/operation/AbstractChangePlanItemInstanceStateOperation.java
+++ b/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/agenda/operation/AbstractChangePlanItemInstanceStateOperation.java
@@ -118,7 +118,9 @@ public String toString() {
             stringBuilder.append(planItem);
         }
 
-        stringBuilder.append(" (PlanItemInstance id: ");
+        stringBuilder.append(" (CaseInstance id: ");
+        stringBuilder.append(planItemInstanceEntity.getCaseInstanceId());
+        stringBuilder.append(", PlanItemInstance id: ");
         stringBuilder.append(planItemInstanceEntity.getId());
         stringBuilder.append("), ");
 
diff --git a/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/agenda/operation/ActivatePlanItemInstanceOperation.java b/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/agenda/operation/ActivatePlanItemInstanceOperation.java
index 471eebdfe5b..1587febf1a5 100644
--- a/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/agenda/operation/ActivatePlanItemInstanceOperation.java
+++ b/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/agenda/operation/ActivatePlanItemInstanceOperation.java
@@ -87,9 +87,11 @@ public String toString() {
         stringBuilder.append("[Activate PlanItem] ");
         stringBuilder.append(planItem);
 
-        stringBuilder.append(" (PlanItemInstance id: ");
+        stringBuilder.append(" (CaseInstance id: ");
+        stringBuilder.append(planItemInstanceEntity.getCaseInstanceId());
+        stringBuilder.append(", PlanItemInstance id: ");
         stringBuilder.append(planItemInstanceEntity.getId());
-        stringBuilder.append(")");
+        stringBuilder.append("), ");
 
         if (entryCriterionId != null) {
             stringBuilder.append(" via entry criterion ").append(entryCriterionId);
diff --git a/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/persistence/entity/CaseInstanceEntityImpl.java b/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/persistence/entity/CaseInstanceEntityImpl.java
index 67282a5741e..b6b3e508296 100644
--- a/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/persistence/entity/CaseInstanceEntityImpl.java
+++ b/modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/persistence/entity/CaseInstanceEntityImpl.java
@@ -489,7 +489,10 @@ public void setCaseDefinitionDeploymentId(String caseDefinitionDeploymentId) {
     public String toString() {
         StringBuilder sb = new StringBuilder();
         sb.append("CaseInstance[id=").append(id)
-                .append(", caseDefinitionId=").append(caseDefinitionId);
+                .append(", caseDefinitionId=").append(caseDefinitionId)
+                .append(", caseDefinitionKey=").append(caseDefinitionKey)
+                .append(", parentId=").append(parentId)
+                .append(", name=").append(name);
 
         if (StringUtils.isNotEmpty(tenantId)) {
             sb.append(", tenantId=").append(tenantId);
diff --git a/modules/flowable-engine/src/main/java/org/flowable/engine/impl/bpmn/behavior/MultiInstanceActivityBehavior.java b/modules/flowable-engine/src/main/java/org/flowable/engine/impl/bpmn/behavior/MultiInstanceActivityBehavior.java
index 8a570056157..12447b2a043 100644
--- a/modules/flowable-engine/src/main/java/org/flowable/engine/impl/bpmn/behavior/MultiInstanceActivityBehavior.java
+++ b/modules/flowable-engine/src/main/java/org/flowable/engine/impl/bpmn/behavior/MultiInstanceActivityBehavior.java
@@ -505,12 +505,33 @@ protected Collection resolveAndValidateCollection(DelegateExecution execution) {
                 }
                 
             } else {
-                throw new FlowableIllegalArgumentException("Couldn't resolve collection expression, variable reference or string");
-                
+                throw new FlowableIllegalArgumentException(buildUnresolvedCollectionExceptionMessage());
             }
         }
     }
-    
+
+    protected String buildUnresolvedCollectionExceptionMessage() {
+        StringBuilder exceptionStringBuilder = new StringBuilder("Couldn't resolve collection expression");
+        if (collectionExpression != null) {
+            exceptionStringBuilder.append(" (");
+            exceptionStringBuilder.append(collectionExpression.getExpressionText());
+            exceptionStringBuilder.append(")");
+        }
+        exceptionStringBuilder.append(", variable reference");
+        if (collectionVariable != null) {
+            exceptionStringBuilder.append(" (");
+            exceptionStringBuilder.append(collectionVariable);
+            exceptionStringBuilder.append(")");
+        }
+        exceptionStringBuilder.append(" or string");
+        if (collectionString != null) {
+            exceptionStringBuilder.append(" (");
+            exceptionStringBuilder.append(collectionString);
+            exceptionStringBuilder.append(")");
+        }
+        return exceptionStringBuilder.toString();
+    }
+
     @SuppressWarnings({ "unchecked", "rawtypes" })
     protected Collection iterableToCollection(Iterable iterable) {
         List result = new ArrayList();