What did you do?

I iterated through gif frames and added copies of the frames converted to rgba to a list of the following 4 frame gif

This was the code I used and what produced the invalid result

frames = []
while True:
    frames.append(im.copy().convert('RGBA'))
    try:
        im.seek(im.tell() + 1)
    except EOFError:
        break

What did you expect to happen?

Expected that all the frames would look normal without them merging

What actually happened?

The last 2 images merged as in the following pic when the expected result would be
The second last frame was kept normal but the last frame included the second last frame merged to it
I was able to get the desired result by using the following modification of my original loop

frames = []
while True:
    frames.append(im.copy().convert('RGBA'))
    try:
        im.seek(im.tell() + 1)
    except EOFError:
        frames[-1] = im.copy().convert('RGBA')
        break

What versions of Pillow and Python are you using?

Python 3.6.4
Pillow 5.1.0