diff --git a/.gitignore b/.gitignore
index 92b5689..1a21d13 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,6 +16,8 @@ invesalius/gui/widgets/*.pyc
 invesalius/reader/*.log
 invesalius/reader/*.pyc
 
+.idea
+
 *.pyc
 *.swp
 *.so
diff --git a/invesalius/data/coordinates.py b/invesalius/data/coordinates.py
index daa0f0e..4635634 100644
--- a/invesalius/data/coordinates.py
+++ b/invesalius/data/coordinates.py
@@ -20,6 +20,7 @@
 from math import sin, cos
 import numpy as np
 
+from time import sleep
 from random import uniform
 
 
@@ -211,7 +212,7 @@ def DebugCoord(trk_init, trck_id, ref_mode):
     :param trck_id: id of tracking device
     :return: six coordinates x, y, z, alfa, beta and gama
     """
-
+    sleep(0.2)
     if ref_mode:
         probe = np.array([uniform(1, 200), uniform(1, 200), uniform(1, 200),
                           uniform(1, 200), uniform(1, 200), uniform(1, 200)])
diff --git a/invesalius/data/coregistration.py b/invesalius/data/coregistration.py
index c82df2a..2098504 100644
--- a/invesalius/data/coregistration.py
+++ b/invesalius/data/coregistration.py
@@ -74,8 +74,8 @@ class Coregistration(threading.Thread):
             # TODO: Optimize the value of sleep for each tracking device.
             # Debug tracker is not working with 0.175 so changed to 0.2
             # However, 0.2 is too low update frequency ~5 Hz. Need optimization URGENTLY.
-            sleep(.3)
-            # sleep(0.175)
+            #sleep(.3)
+            sleep(0.175)
 
             if self._pause_:
                 return
diff --git a/invesalius/data/viewer_volume.py b/invesalius/data/viewer_volume.py
index 5fa6bca..dfd3602 100755
--- a/invesalius/data/viewer_volume.py
+++ b/invesalius/data/viewer_volume.py
@@ -674,7 +674,8 @@ class Viewer(wx.Panel):
         # Need to be outside condition for sphere marker position update
         # self.ren.ResetCameraClippingRange()
         # self.ren.ResetCamera()
-        self.interactor.Render()
+        #self.interactor.Render()
+        self.Refresh()
 
     def OnExportSurface(self, pubsub_evt):
         filename, filetype = pubsub_evt.data
diff --git a/invesalius/gui/task_navigator.py b/invesalius/gui/task_navigator.py
index ad8f8eb..73c786f 100644
--- a/invesalius/gui/task_navigator.py
+++ b/invesalius/gui/task_navigator.py
@@ -141,7 +141,7 @@ class InnerFoldPanel(wx.Panel):
         fold_panel.AddFoldPanelWindow(item, mtw, Spacing= 0,
                                       leftSpacing=0, rightSpacing=0)
 
-        
+
         # Check box for camera update in volume rendering during navigation
         tooltip = wx.ToolTip(_("Update camera in volume"))
         checkcamera = wx.CheckBox(self, -1, _('Volume camera'))
@@ -174,7 +174,7 @@ class InnerFoldPanel(wx.Panel):
         self.SetSizer(sizer)
         self.Update()
         self.SetAutoLayout(1)
-        
+
     def UpdateExternalTrigger(self, evt, ctrl):
         Publisher.sendMessage('Update trigger state', ctrl.GetValue())
 
@@ -633,23 +633,28 @@ class MarkersPanel(wx.Panel):
                 for id_n in range(self.lc.GetItemCount()):
                     item = self.lc.GetItem(id_n, 4)
                     if item.GetText() == marker_id:
-                        if marker_id == "LEI" or marker_id == "REI" or marker_id == "NAI":
-                            self.lc.Focus(item.GetId())
-                            break
+                        for i in const.BTNS_IMG:
+                            if marker_id in const.BTNS_IMG[i].values()[0]:
+                                self.lc.Focus(item.GetId())
+                                break
+                self.DeleteMarker()
         else:
-            if self.lc.GetFocusedItem() is not -1 and self.lc.GetItemCount():
-                index = self.lc.GetFocusedItem()
-                del self.list_coord[index]
-                self.lc.DeleteItem(index)
-                for n in range(0, self.lc.GetItemCount()):
-                    self.lc.SetStringItem(n, 0, str(n+1))
-                self.marker_ind -= 1
-                Publisher.sendMessage('Remove marker', index)
+            if self.lc.GetFocusedItem() is not -1:
+                self.DeleteMarker()
             elif not self.lc.GetItemCount():
                 pass
             else:
                 dlg.NoMarkerSelected()
 
+    def DeleteMarker(self):
+        index = self.lc.GetFocusedItem()
+        del self.list_coord[index]
+        self.lc.DeleteItem(index)
+        for n in range(0, self.lc.GetItemCount()):
+            self.lc.SetStringItem(n, 0, str(n+1))
+        self.marker_ind -= 1
+        Publisher.sendMessage('Remove marker', index)
+
     def OnCreateMarker(self, evt):
         # OnCreateMarker is used for both pubsub and button click events
         # Pubsub is used for markers created with fiducial buttons, trigger and create marker button
@@ -674,8 +679,9 @@ class MarkersPanel(wx.Panel):
                     size = float(line[6])
 
                     if len(line) == 8:
-                        if line[7] == "LEI" or line[7] == "REI" or line[7] == "NAI":
-                            Publisher.sendMessage('Load image fiducials', (line[7], coord))
+                        for i in const.BTNS_IMG:
+                            if line[7] in const.BTNS_IMG[i].values()[0]:
+                                Publisher.sendMessage('Load image fiducials', (line[7], coord))
                     else:
                         line.append("")
                     self.CreateMarker(coord, colour, size, line[7])
@@ -690,7 +696,7 @@ class MarkersPanel(wx.Panel):
         else:
             Publisher.sendMessage('Show all markers',  self.lc.GetItemCount())
             ctrl.SetLabel('Hide')
-            
+
     def OnSaveMarkers(self, evt):
         filename = dlg.ShowSaveMarkersDialog("markers.txt")
         if filename:
@@ -709,7 +715,7 @@ class MarkersPanel(wx.Panel):
 
                 text_file.writelines(line)
                 text_file.close()
-    
+
     def OnSelectColour(self, evt, ctrl):
         self.marker_colour = [colour/255.0 for colour in ctrl.GetValue()]
 
--
libgit2 0.21.2