diff --git a/build-flags/build_flags_due b/build-flags/build_flags_due
index 9c1c133..a9612ed 100644
--- a/build-flags/build_flags_due
+++ b/build-flags/build_flags_due
@@ -1,7 +1,7 @@
 #-DW5500_CS_PIN=53
 -DDMX_SMOOTH
 -DSYSLOG_ENABLE
--DMODBUS_DIMMER_PARAM=SERIAL_8E1
+#-DMODBUS_DIMMER_PARAM=SERIAL_8E1
 -DARTNET_ENABLE
 -DOTA
 -DSTATUSLED
diff --git a/build-flags/build_flags_mega2560-5100 b/build-flags/build_flags_mega2560-5100
index 6eea03c..ba410e1 100644
--- a/build-flags/build_flags_mega2560-5100
+++ b/build-flags/build_flags_mega2560-5100
@@ -1,4 +1,4 @@
--DMODBUS_DIMMER_PARAM=SERIAL_8E1
+#-DMODBUS_DIMMER_PARAM=SERIAL_8E1
 -DAVR_DMXOUT_PIN=18
 -DSYSLOG_ENABLE
 -DWiz5100
diff --git a/build-flags/build_flags_mega2560-5500 b/build-flags/build_flags_mega2560-5500
index b67a117..dc93f63 100644
--- a/build-flags/build_flags_mega2560-5500
+++ b/build-flags/build_flags_mega2560-5500
@@ -1,5 +1,5 @@
 -DWiz5500
--DMODBUS_DIMMER_PARAM=SERIAL_8E1
+#-DMODBUS_DIMMER_PARAM=SERIAL_8E1
 -DAVR_DMXOUT_PIN=18
 -DSYSLOG_ENABLE
 #-DPID_DISABLE
\ No newline at end of file
diff --git a/build-flags/build_flags_mega2560slim-5100 b/build-flags/build_flags_mega2560slim-5100
index 54b7a7d..d893974 100644
--- a/build-flags/build_flags_mega2560slim-5100
+++ b/build-flags/build_flags_mega2560slim-5100
@@ -13,3 +13,4 @@
 -DAC_DISABLE
 -DSYSLOG_ENABLE
 -DPID_DISABLE
+-DWiz5100
\ No newline at end of file
diff --git a/lighthub/item.cpp b/lighthub/item.cpp
index 682d71a..b20b894 100644
--- a/lighthub/item.cpp
+++ b/lighthub/item.cpp
@@ -1391,8 +1391,8 @@ int Item::modbusDimmerSet(itemCmd st)
         }
 #endif
 
-void Item::mb_fail() {
-    debugSerial<<F("Modbus op failed\n");
+void Item::mb_fail(int result) {
+    debugSerial<<F("Modbus op failed:")<<_HEX(result)<<endl;
     setFlag(SEND_RETRY);
 }
 
@@ -1440,7 +1440,7 @@ int Item::VacomSetFan(itemCmd st) {
     modbusBusy = 0;
 
     if (result == node.ku8MBSuccess) return 1;
-    mb_fail();
+    mb_fail(result);
     return 0;
 }
 
@@ -1490,7 +1490,7 @@ int addr;
     result=node.writeSingleRegister(2004 - 1, regval);
     modbusBusy = 0;
     if (result == node.ku8MBSuccess) return 1;
-    mb_fail();
+    mb_fail(result);
     return 0;
 
 }
@@ -1532,7 +1532,7 @@ int Item::modbusDimmerSet(int addr, uint16_t _reg, int _regType, int _mask, uint
     modbusBusy = 0;
 
     if (result == node.ku8MBSuccess) return 1;
-    mb_fail();
+    mb_fail(result);
     return 0;
 
 }
diff --git a/lighthub/item.h b/lighthub/item.h
index 4f2b7b1..e7804b8 100644
--- a/lighthub/item.h
+++ b/lighthub/item.h
@@ -143,7 +143,7 @@ class Item
   int modbusDimmerSet(itemCmd st);
 
   int modbusDimmerSet(int addr, uint16_t _reg, int _regType, int _mask, uint16_t value);
-  void mb_fail();
+  void mb_fail(int result=0);
   void Parse();
   int checkModbusDimmer();
   int checkModbusDimmer(int data);
diff --git a/lighthub/modules/out_modbus.cpp b/lighthub/modules/out_modbus.cpp
index 8dc790e..af380a4 100644
--- a/lighthub/modules/out_modbus.cpp
+++ b/lighthub/modules/out_modbus.cpp
@@ -101,7 +101,7 @@ int  str2regSize(char * str)
 bool out_Modbus::getConfig()
 {
   // Retrieve and store template values from global modbus settings
-  if (!store || !item || !item->itemArg || (item->itemArg->type != aJson_Array) || aJson.getArraySize(item->itemArg)<2)
+  if (!store || !item || !item->itemArg || (item->itemArg->type != aJson_Array) || aJson.getArraySize(item->itemArg)<2 || !modbusObj)
   {
     errorSerial<<F("MBUS: config failed:")<<(bool)store<<F(",")<<(bool)item<<F(",")<<(bool)item->itemArg<<F(",")<<(item->itemArg->type != aJson_Array)<<F(",")<< (aJson.getArraySize(item->itemArg)<2)<<endl;
     return false;
@@ -216,7 +216,7 @@ switch (regType) {
     default:
         debugSerial<<F("Not supported reg type\n");
  }
-if (result != node.ku8MBSuccess) errorSerial<<F("MBUS: Polling error ")<<result<<endl;
+if (result != node.ku8MBSuccess) errorSerial<<F("MBUS: Polling error ")<<_HEX(result)<<endl;
 return (result == node.ku8MBSuccess);
 }