diff --git a/cura/CuraApplication.py b/cura/CuraApplication.py
index c2a08cadfc..d5f90f6846 100644
--- a/cura/CuraApplication.py
+++ b/cura/CuraApplication.py
@@ -866,7 +866,7 @@ class CuraApplication(QtApplication):
             return
 
         # Compute the center of the objects when their origins are aligned.
-        object_centers = [node.getMeshData().getCenterPosition().scale(node.getScale()) for node in group_node.getChildren() if node.getMeshData()]
+        object_centers = [node.getBoundingBox().center for node in group_node.getChildren()]
         if object_centers and len(object_centers) > 0:
             middle_x = sum([v.x for v in object_centers]) / len(object_centers)
             middle_y = sum([v.y for v in object_centers]) / len(object_centers)
@@ -874,11 +874,10 @@ class CuraApplication(QtApplication):
             offset = Vector(middle_x, middle_y, middle_z)
         else:
             offset = Vector(0, 0, 0)
-
         # Move each node to the same position.
         for center, node in zip(object_centers, group_node.getChildren()):
             # Align the object and also apply the offset to center it inside the group.
-            node.setPosition(center - offset)
+            node.translate(-1 * (center - offset), SceneNode.TransformSpace.World)
 
         # Use the previously found center of the group bounding box as the new location of the group
         group_node.setPosition(group_node.getBoundingBox().center)
diff --git a/plugins/3MFReader/ThreeMFReader.py b/plugins/3MFReader/ThreeMFReader.py
index 633eb8bb02..a06c557276 100644
--- a/plugins/3MFReader/ThreeMFReader.py
+++ b/plugins/3MFReader/ThreeMFReader.py
@@ -17,6 +17,7 @@ import zipfile
 try:
     import xml.etree.cElementTree as ET
 except ImportError:
+    Logger.log("w", "Unable to load cElementTree, switching to slower version")
     import xml.etree.ElementTree as ET
 
 ##    Base implementation for reading 3MF files. Has no support for textures. Only loads meshes!
diff --git a/plugins/USBPrinting/USBPrinterOutputDevice.py b/plugins/USBPrinting/USBPrinterOutputDevice.py
index 6147bfb53f..13dfe967b3 100644
--- a/plugins/USBPrinting/USBPrinterOutputDevice.py
+++ b/plugins/USBPrinting/USBPrinterOutputDevice.py
@@ -19,7 +19,6 @@ from PyQt5.QtCore import QUrl, pyqtSlot, pyqtSignal, pyqtProperty
 from UM.i18n import i18nCatalog
 catalog = i18nCatalog("cura")
 
-
 class USBPrinterOutputDevice(PrinterOutputDevice):
 
     def __init__(self, serial_port):
diff --git a/plugins/USBPrinting/avr_isp/intelHex.py b/plugins/USBPrinting/avr_isp/intelHex.py
index 6e27595587..a51c798d8e 100644
--- a/plugins/USBPrinting/avr_isp/intelHex.py
+++ b/plugins/USBPrinting/avr_isp/intelHex.py
@@ -7,7 +7,6 @@ This is a python 3 conversion of the code created by David Braam for the Cura pr
 import io
 from UM.Logger import Logger
 
-
 def readHex(filename):
     """
     Read an verify an intel hex file. Return the data as an list of bytes.
diff --git a/plugins/USBPrinting/avr_isp/stk500v2.py b/plugins/USBPrinting/avr_isp/stk500v2.py
index 3bbecb06c2..ccbaa3de53 100644
--- a/plugins/USBPrinting/avr_isp/stk500v2.py
+++ b/plugins/USBPrinting/avr_isp/stk500v2.py
@@ -3,7 +3,6 @@ STK500v2 protocol implementation for programming AVR chips.
 The STK500v2 protocol is used by the ArduinoMega2560 and a few other Arduino platforms to load firmware.
 This is a python 3 conversion of the code created by David Braam for the Cura project.
 """
-import os
 import struct
 import sys
 import time
@@ -28,7 +27,7 @@ class Stk500v2(ispBase.IspBase):
             self.close()
         try:
             self.serial = Serial(str(port), speed, timeout=1, writeTimeout=10000)
-        except SerialException as e:
+        except SerialException:
             raise ispBase.IspError("Failed to open serial port")
         except:
             raise ispBase.IspError("Unexpected error while connecting to serial port:" + port + ":" + str(sys.exc_info()[0]))
@@ -92,7 +91,7 @@ class Stk500v2(ispBase.IspBase):
             self.sendMessage([0x06, 0x00, 0x00, 0x00, 0x00])
         load_count = (len(flash_data) + page_size - 1) / page_size
         for i in range(0, int(load_count)):
-            recv = self.sendMessage([0x13, page_size >> 8, page_size & 0xFF, 0xc1, 0x0a, 0x40, 0x4c, 0x20, 0x00, 0x00] + flash_data[(i * page_size):(i * page_size + page_size)])
+            self.sendMessage([0x13, page_size >> 8, page_size & 0xFF, 0xc1, 0x0a, 0x40, 0x4c, 0x20, 0x00, 0x00] + flash_data[(i * page_size):(i * page_size + page_size)])
             if self.progress_callback is not None:
                 if self._has_checksum:
                     self.progress_callback(i + 1, load_count)
@@ -183,11 +182,11 @@ class Stk500v2(ispBase.IspBase):
 def portList():
     ret = []
     import _winreg
-    key=_winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE,"HARDWARE\\DEVICEMAP\\SERIALCOMM")
+    key=_winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE,"HARDWARE\\DEVICEMAP\\SERIALCOMM") #@UndefinedVariable
     i=0
     while True:
         try:
-            values = _winreg.EnumValue(key, i)
+            values = _winreg.EnumValue(key, i) #@UndefinedVariable
         except:
             return ret
         if "USBSER" in values[0]:
@@ -206,7 +205,7 @@ def main():
     """ Entry point to call the stk500v2 programmer from the commandline. """
     import threading
     if sys.argv[1] == "AUTO":
-        Logger.log("d", portList())
+        Logger.log("d", "portList(): ", repr(portList()))
         for port in portList():
             threading.Thread(target=runProgrammer, args=(port,sys.argv[2])).start()
             time.sleep(5)