Possible combustion in Model 2

[CMack150]

The last two times I have smoked something in my model 2, about 20 minutes in, the smoke starts to puff out the top a few times and then instantly no smoke.  Then suddenly a flame shoots out of the top hole of the smoker and you hear a loud noise.  Smoke rushes out of the top hole and from around the door.  Everything seems fine inside the smoker after this and I assume the loud noise is from the smoke box top flying open and the box shuttering.  Any ideas of why this is occurring or any suggestions?  Thanks

Chris

 

[old sarge]

I have experienced the "burp" in both the Smokin-it and the Cookshack as the gasses/wood combusted.  Never had flame shooting out the vent. Never had any bitterness in the meat.

 

[Lonzinomaker]

Make sure you didn't forget to punch a hole in the foil on the bottom where the drain hole is.
I made boats out of aluminum flashing to slow the combustion in my smokers (see this thread-https://www.smokinitforums.com/index.php?topic=8436.msg72994#msg72994)