diff --git a/cura/Settings/GlobalStack.py b/cura/Settings/GlobalStack.py
index cc3a29aa8b..6d18bf615b 100755
--- a/cura/Settings/GlobalStack.py
+++ b/cura/Settings/GlobalStack.py
@@ -1,6 +1,8 @@
 # Copyright (c) 2017 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from collections import defaultdict
+import threading
 from typing import Any, Dict, Optional
 
 from PyQt5.QtCore import pyqtProperty
@@ -30,8 +32,8 @@ class GlobalStack(CuraContainerStack):
         # This property is used to track which settings we are calculating the "resolve" for
         # and if so, to bypass the resolve to prevent an infinite recursion that would occur
         # if the resolve function tried to access the same property it is a resolve for.
-        self._resolving_settings = set()
-        self._resolving_settings2 = []  # For debugging CURA-4848, if it happens
+        # Per thread we have our own resolving_settings, or strange things sometimes occur.
+        self._resolving_settings = defaultdict(set)  # keys are thread names
 
     ##  Get the list of extruders of this stack.
     #
@@ -92,17 +94,10 @@ class GlobalStack(CuraContainerStack):
 
         # Handle the "resolve" property.
         if self._shouldResolve(key, property_name, context):
-            self._resolving_settings2.append(key)
-            self._resolving_settings.add(key)
+            current_thread = threading.current_thread()
+            self._resolving_settings[current_thread.name].add(key)
             resolve = super().getProperty(key, "resolve", context)
-            if key not in self._resolving_settings:
-                Logger.log("e", "Key [%s] should really have been in set(%s) and [%s]. Now I'm gonna crash", key, str(self._resolving_settings), str(self._resolving_settings2))
-                Logger.log("d", "------ context ------")
-                for stack in context.stack_of_containers:
-                    Logger.log("d", "Context: %s", stack.getId())
-                Logger.log("d", "------ context end ------")
-            self._resolving_settings.remove(key)
-            self._resolving_settings2.pop()
+            self._resolving_settings[current_thread.name].remove(key)
             if resolve is not None:
                 return resolve
 
@@ -154,7 +149,8 @@ class GlobalStack(CuraContainerStack):
             # Do not try to resolve anything but the "value" property
             return False
 
-        if key in self._resolving_settings:
+        current_thread = threading.current_thread()
+        if key in self._resolving_settings[current_thread.name]:
             # To prevent infinite recursion, if getProperty is called with the same key as
             # we are already trying to resolve, we should not try to resolve again. Since
             # this can happen multiple times when trying to resolve a value, we need to
diff --git a/plugins/PluginBrowser/PluginBrowser.py b/plugins/PluginBrowser/PluginBrowser.py
index 35b88b3465..13fa553779 100644
--- a/plugins/PluginBrowser/PluginBrowser.py
+++ b/plugins/PluginBrowser/PluginBrowser.py
@@ -25,7 +25,7 @@ class PluginBrowser(QObject, Extension):
     def __init__(self, parent=None):
         super().__init__(parent)
 
-        self._api_version = 2
+        self._api_version = 4
         self._api_url = "http://software.ultimaker.com/cura/v%s/" % self._api_version
 
         self._plugin_list_request = None
diff --git a/resources/definitions/fdmprinter.def.json b/resources/definitions/fdmprinter.def.json
index f792731022..aef5533ead 100644
--- a/resources/definitions/fdmprinter.def.json
+++ b/resources/definitions/fdmprinter.def.json
@@ -5339,7 +5339,7 @@
                 },
                 "infill_enable_travel_optimization":
                 {
-                    "label": "Enable Travel Optimization",
+                    "label": "Infill Travel Optimization",
                     "description": "When enabled, the order in which the infill lines are printed is optimized to reduce the distance travelled. The reduction in travel time achieved very much depends on the model being sliced, infill pattern, density, etc. Note that, for some models that have many small areas of infill, the time to slice the model may be greatly increased.",
                     "type": "bool",
                     "default_value": false,