Notebook Cell outputs getting duplicated

[DonJayamanne]

Run the following in a cell and sometimes the numbers get duplicated

def doit():
    counter = 1
    while True:
        import time
        time.sleep(0.1)

        counter = counter + 1
        print(counter)

        if counter > 5:
            break

doit()

The outputs in the JSON are not duplicated leading me to assume this is a rendering issue.
I.e. the output items aren't duplicated in the notebook cell model.

[DonJayamanne]

Unfortunately not easy to repro,

[amunger]

About how often does that happen? I can't seem to repro at all

is it all one output in the json? (I've seen streaming outputs get split in two in the past, not sure why)

[DonJayamanne]

I ran into this just a couple of times yesterday in the same notebook,
couldnt' repro after that, cannot repro today either.
Will keep trying to see if I can get a consistent repro step (FYI, I believe Peng and Michael ran into this in the past as well, but not consistent)