PiCamera start_preview blocks indefinitely

[palu3492]

PiCamera 1.13
Linux raspberrypi 5.10.103+ #1529 Tue Mar 8 12:19:18 GMT 2022 armv6l GNU/Linux

Just came across an issue where PiCamera.start_preview() blocked indefinitely and never returned. I inspected the thread and found it's stuck in the close method of mmalobj.py.

frame = sys._current_frames().get(my_thread.ident, None)
print(frame.f_code.co_filename, frame.f_code.co_name, frame.f_code.co_firstlineno)
('/usr/lib/python2.7/dist-packages/picamera/mmalobj.py', 'close', 663)

Any idea how I can prevent this in the future?