diff --git a/dronecan/node.py b/dronecan/node.py
index 3e504dd..00e970a 100644
--- a/dronecan/node.py
+++ b/dronecan/node.py
@@ -95,12 +95,23 @@ def periodic(self, period_seconds, callback):
         :returns: EventHandle object. Call .remove() on it to cancel the event.
         """
         priority = 0
+        callback_running = [False]  # Use list to allow modification in nested function
 
         def caller(scheduled_deadline):
-            # Event MUST be re-registered first in order to ensure that it can be cancelled from the callback
+            # Always reschedule first to maintain periodic timing
             scheduled_deadline += period_seconds
             event_holder[0] = self._scheduler.enterabs(scheduled_deadline, priority, caller, (scheduled_deadline,))
-            callback()
+            
+            # Prevent callback overlap that can cause runaway scheduling
+            if callback_running[0]:
+                # Skip this execution if previous callback is still running
+                return
+            
+            callback_running[0] = True
+            try:
+                callback()
+            finally:
+                callback_running[0] = False
 
         first_deadline = self._scheduler.timefunc() + period_seconds
         event_holder = [self._scheduler.enterabs(first_deadline, priority, caller, (first_deadline,))]
@@ -438,7 +449,9 @@ def execute_once():
             while time.monotonic() < deadline:
                 execute_once()
         else:
-            while True:
+            # Process available frames with a reasonable limit to prevent GUI blocking
+            max_frames_per_spin = 100  # Limit frames processed per spin(0) call
+            while count < max_frames_per_spin:
                 frame = self._can_driver.receive(0)
                 if frame:
                     self._recv_frame(frame)
diff --git a/dronecan/transport.py b/dronecan/transport.py
index 56bd35e..66ee709 100644
--- a/dronecan/transport.py
+++ b/dronecan/transport.py
@@ -25,6 +25,9 @@
 import dronecan
 import dronecan.dsdl as dsdl
 import dronecan.dsdl.common as common
+from logging import getLogger
+
+logger = getLogger(__name__)
 
 
 try:
@@ -893,9 +896,18 @@ def __init__(self):
     def receive_frame(self, frame):
         result = None
         key = frame.transfer_key
+        
+        # Clean up any stale transfers before processing new frames
+        self.remove_inactive_transfers(timeout=0.1)  # Much shorter timeout
+        
         if key in self.active_transfers or frame.start_of_transfer:
             # If the first frame was received, restart this transfer from scratch
             if frame.start_of_transfer:
+                if key in self.active_transfers:
+                    # Log when we're restarting an incomplete transfer (only for debugging)
+                    # logger.debug('Restarting incomplete transfer for key %r (had %d frames)', 
+                    #            key, len(self.active_transfers[key]))
+                    pass
                 self.active_transfers[key] = []
 
             self.active_transfers[key].append(frame)
@@ -911,7 +923,7 @@ def receive_frame(self, frame):
 
     def remove_inactive_transfers(self, timeout=1.0):
         t = time.monotonic()
-        transfer_keys = self.active_transfers.keys()
+        transfer_keys = list(self.active_transfers.keys())  # Create a copy to avoid iteration issues
         for key in transfer_keys:
             if t - self.active_transfer_timestamps[key] > timeout:
                 del self.active_transfers[key]