diff --git a/cura/PrinterOutput/UploadMaterialsJob.py b/cura/PrinterOutput/UploadMaterialsJob.py
index d000d1ba2d..b082b47cbb 100644
--- a/cura/PrinterOutput/UploadMaterialsJob.py
+++ b/cura/PrinterOutput/UploadMaterialsJob.py
@@ -18,7 +18,7 @@ from UM.Signal import Signal
 from UM.TaskManagement.HttpRequestManager import HttpRequestManager  # To call the API.
 from UM.TaskManagement.HttpRequestScope import JsonDecoratorScope
 
-from typing import Dict, Optional, TYPE_CHECKING
+from typing import Any, Dict, Optional, TYPE_CHECKING
 if TYPE_CHECKING:
     from PyQt5.QtNetwork import QNetworkReply
     from cura.UltimakerCloud.CloudMaterialSync import CloudMaterialSync
@@ -42,7 +42,7 @@ class UploadMaterialsJob(Job):
     UPLOAD_CONFIRM_URL = UltimakerCloudConstants.CuraCloudAPIRoot + "/connect/v1/clusters/{cluster_id}/printers/{cluster_printer_id}/action/confirm_material_upload"
 
     class Result(enum.IntEnum):
-        SUCCCESS = 0
+        SUCCESS = 0
         FAILED = 1
 
     def __init__(self, material_sync: "CloudMaterialSync"):
@@ -51,8 +51,8 @@ class UploadMaterialsJob(Job):
         self._scope = JsonDecoratorScope(UltimakerCloudScope(cura.CuraApplication.CuraApplication.getInstance()))  # type: JsonDecoratorScope
         self._archive_filename = None  # type: Optional[str]
         self._archive_remote_id = None  # type: Optional[str]  # ID that the server gives to this archive. Used to communicate about the archive to the server.
-        self._printer_sync_status = {}
-        self._printer_metadata = {}
+        self._printer_sync_status = {}  # type: Dict[str, str]
+        self._printer_metadata = {}  # type: Dict[str, Any]
         self.processProgressChanged.connect(self._onProcessProgressChanged)
 
     uploadCompleted = Signal()
@@ -113,7 +113,8 @@ class UploadMaterialsJob(Job):
 
         upload_url = response_data["upload_url"]
         self._archive_remote_id = response_data["material_profile_id"]
-        file_data = open(self._archive_filename, "rb").read()
+        with open(self._archive_filename, "rb") as f:
+            file_data = f.read()
         http = HttpRequestManager.getInstance()
         http.put(
             url = upload_url,
diff --git a/cura/UltimakerCloud/CloudMaterialSync.py b/cura/UltimakerCloud/CloudMaterialSync.py
index 99282d7eb1..3a9402c36e 100644
--- a/cura/UltimakerCloud/CloudMaterialSync.py
+++ b/cura/UltimakerCloud/CloudMaterialSync.py
@@ -27,8 +27,8 @@ class CloudMaterialSync(QObject):
         self.sync_all_dialog = None  # type: Optional[QObject]
         self._export_upload_status = "idle"
         self._checkIfNewMaterialsWereInstalled()
-        self._export_progress = 0
-        self._printer_status = {}
+        self._export_progress = 0.0
+        self._printer_status = {}  # type: Dict[str, str]
 
     def _checkIfNewMaterialsWereInstalled(self) -> None:
         """
@@ -161,6 +161,8 @@ class CloudMaterialSync(QObject):
         self.setPrinterStatus(printers_status)
 
     def exportUploadCompleted(self, job_result: UploadMaterialsJob.Result, job_error: Optional[Exception]):
+        if not self.sync_all_dialog:  # Shouldn't get triggered before the dialog is open, but better to check anyway.
+            return
         if job_result == UploadMaterialsJob.Result.FAILED:
             if isinstance(job_error, UploadMaterialsError):
                 self.sync_all_dialog.setProperty("syncStatusText", catalog.i18nc("@text", "Error sending materials to the Digital Factory:") + " " + str(job_error))
diff --git a/cura/UltimakerCloud/UltimakerCloudScope.py b/cura/UltimakerCloud/UltimakerCloudScope.py
index c8ac35f893..bbcc8e2aa9 100644
--- a/cura/UltimakerCloud/UltimakerCloudScope.py
+++ b/cura/UltimakerCloud/UltimakerCloudScope.py
@@ -5,11 +5,11 @@ from PyQt5.QtNetwork import QNetworkRequest
 
 from UM.Logger import Logger
 from UM.TaskManagement.HttpRequestScope import DefaultUserAgentScope
-from cura.API import Account
 
 from typing import TYPE_CHECKING
 if TYPE_CHECKING:
     from cura.CuraApplication import CuraApplication
+    from cura.API.Account import Account
 
 
 class UltimakerCloudScope(DefaultUserAgentScope):