Qt5Gui.dll silently crashes with error code 0xc0000005

Good afternoon,

I'm encountering an issue while using PyQt5 v5.15.1 and v5.15.2 with the 'pyqtSignal' silently crashing my application. I'm using Python 3.8.5 in an Anaconda environment and the crash produces no error with Python just exiting.

I looked into Windows's event viewer and saw that the dll responsible for the crash was Qt5Gui.dll with the error code 0xc0000005.

I've attached a minimum-reproducible example. Here are some other considerations about my application you might need:

• It is threaded with Qt's QThread class. The 'pyqtSignal' crashing the application is not communicating across threads, QThreads, or processes, however.
• It is also multi-processed using Python's stdlib 'Process' class.
• The function I am connecting to is decorated with the 'pyqtSlot' decorator. The data being sent through the signal is the sender. I tried sending a simple 12-character string id through the signal as well; however, it also crashed. For the class, the 'pyqtSlot' decorator was '@pyqtSlot(object)'; for the string, it was '@pyqtSlot(str)'. The signal used the same types as the slot.
• There may upwards of 100 connections to this receiver function; however, the dll is crashing with only about 25.
• The application crashes while in src and bundled with PyInstaller (as a .exe).
• The sender is subclassing Qt's 'QLabel'. The receiver class is subclassing Qt's 'QObject'.

Please let me know if there is anything else I need provide.