diff --git a/octoprint_bambu_printer/printer/bambu_virtual_printer.py b/octoprint_bambu_printer/printer/bambu_virtual_printer.py
index d24b0fa..6633920 100644
--- a/octoprint_bambu_printer/printer/bambu_virtual_printer.py
+++ b/octoprint_bambu_printer/printer/bambu_virtual_printer.py
@@ -272,12 +272,7 @@ class BambuVirtualPrinter:
         return self._serial_io.readline()
 
     def readlines(self) -> list[bytes]:
-        result = []
-        next_line = self._serial_io.readline()
-        while next_line != b"":
-            result.append(next_line)
-            next_line = self._serial_io.readline()
-        return result
+        return self._serial_io.readlines()
 
     def sendIO(self, line: str):
         self._serial_io.send(line)
@@ -504,24 +499,10 @@ class BambuVirtualPrinter:
         self._writingToSdFile = None
         self.sendIO("Done saving file")
 
-    def _setMainThreadBusy(self, reason="processing"):
-        def loop():
-            while self._busy_reason is not None:
-                self.sendIO(f"echo:busy {self._busy_reason}")
-                time.sleep(self._busy_interval)
-            self._serial_io.sendOk()
-
-        self._busy_reason = reason
-        self._busy_loop = threading.Thread(target=loop)
-        self._busy_loop.daemon = True
-        self._busy_loop.start()
-
-    def _setMainThreadIdle(self):
-        self._busy_reason = None
-
     def close(self):
         if self.bambu_client.connected:
             self.bambu_client.disconnect()
+        self.change_state(self._state_idle)
         self._serial_io.close()
 
     def _showPrompt(self, text, choices):
diff --git a/octoprint_bambu_printer/printer/printer_serial_io.py b/octoprint_bambu_printer/printer/printer_serial_io.py
index 0a9e877..7ce55d5 100644
--- a/octoprint_bambu_printer/printer/printer_serial_io.py
+++ b/octoprint_bambu_printer/printer/printer_serial_io.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from io import BufferedIOBase
 import logging
 import queue
 import re
@@ -13,7 +14,7 @@ from serial import SerialTimeoutException
 from .char_counting_queue import CharCountingQueue
 
 
-class PrinterSerialIO(threading.Thread):
+class PrinterSerialIO(threading.Thread, BufferedIOBase):
     command_regex = re.compile(r"^([GM])(\d+)")
 
     def __init__(
@@ -90,8 +91,7 @@ class PrinterSerialIO(threading.Thread):
         self.join()
 
     def flush(self):
-        with self.input_bytes.all_tasks_done:
-            self.input_bytes.all_tasks_done.wait()
+        self.input_bytes.join()
 
     def write(self, data: bytes) -> int:
         data = to_bytes(data, errors="replace")
@@ -126,6 +126,14 @@ class PrinterSerialIO(threading.Thread):
             # queue empty? return empty line
             return b""
 
+    def readlines(self):
+        result = []
+        next_line = self.readline()
+        while next_line != b"":
+            result.append(next_line)
+            next_line = self.readline()
+        return result
+
     def send(self, line: str) -> None:
         if self.output_bytes is not None:
             self.output_bytes.put(line)
diff --git a/octoprint_bambu_printer/printer/states/print_finished_state.py b/octoprint_bambu_printer/printer/states/print_finished_state.py
index dce0684..d0acf5b 100644
--- a/octoprint_bambu_printer/printer/states/print_finished_state.py
+++ b/octoprint_bambu_printer/printer/states/print_finished_state.py
@@ -12,8 +12,5 @@ class PrintFinishedState(APrinterState):
     def _finishSdPrint(self):
         if self._printer.is_running:
             self._printer.sendIO("Done printing file")
-            self._selectedSdFilePos = 0
-            self._selectedSdFileSize = 0
-            self._sdPrinting = False
-            self._sdPrintStarting = False
-            self._sdPrinter = None
+
+        self._printer.change_state(self._printer._state_idle)
diff --git a/test/test_gcode_execution.py b/test/test_gcode_execution.py
index c56affd..9fcbbfe 100644
--- a/test/test_gcode_execution.py
+++ b/test/test_gcode_execution.py
@@ -133,7 +133,8 @@ def printer(output_test_folder, settings, profile_manager, log_test, ftps_sessio
         faked_baudrate=115200,
     )
     serial_obj._bambu_client = MagicMock()
-    return serial_obj
+    yield serial_obj
+    serial_obj.close()
 
 
 def test_initial_state(printer: BambuVirtualPrinter):
@@ -142,7 +143,7 @@ def test_initial_state(printer: BambuVirtualPrinter):
 
 def test_list_sd_card(printer: BambuVirtualPrinter):
     printer.write(b"M20\n")  # GCode for listing SD card
-    printer.close()
+    printer.flush()
     result = printer.readlines()
     assert result == ""  # Replace with the actual expected result