As per this book (some of my "light reading"):
The "official" lab name for burping is called bumping and it happens with a lot of liquids during evaporation. The molecules in the liquid expand and evaporate faster than the ones on top and since the liquid is a bit thicker you get these "eruptions".
Several things can be done to reduce bumping:
1. Have precise temperature control; with the PIC you should be able to come down from 180 to 175 to 170 and 160 if needed. Usually only 10 degree increments are available but medium low is 175.
2. use "evaporation stones"; these are like a small golf ball and increase the surface are to promote the formation of bubbles. I recommend you use a handful of large marbles and just throw them in there.
I use my Nuwave oven on power level 6 to decarb. It outputs a very precise 250*F (+/- 5*F) and only takes 3 minutes to preheat so I just add 3 minutes to my time.
Thanks. My wife does the chemistry. She is a MT, chemist and biologist by degrees. She has managed a lab for 25 years.
If there is no plant material in your alcohol oil mixture it won't burp, as I experienced it in my second attempt at making my oil when refiltering stopped the burping. In my error I didn't filter the third wash after straining the muslin bag of material, my only part in making my oil. A lot of plant material was left in alcohol oil mixture. My first attempt at making oil, I filtered properly and had no burping. When I filtered properly this time I had no burping. So your explanation probably explains some burping cases but in my case, I think it was the plant material.
I'll have to try decarbing in my oven or on the PIC2. Can't afford to buy another product from NuWave for a while.