FifoDiskQueue Size is Getting Bigger

[DavidDr90]

I'm trying to implement a fixed size queue using FifoDiskQueue.
My code is:

self._images_data = FifoDiskQueue(r"c:\temp")
...
# this code is inside a loop
# implement fixed size queue
if len(self._images_data) >= 400:
      self._images_data.pop()
self._images_data.push(frame.tobytes()) # add the new frame to the main data base
...
# after the while ends running:
self._images_data.close()

I'm seeing two issues:

1. While the main loop is running the queue file q00000 is always 0 KB
2. My memory is decreasing meaning the queue is keep getting bigger and bigger although I'm "pop" out any old element before adding new one

Can some help me figure out why the size keep getting bigger or point me to the right way to implement a fixed size queue?