I suspect this is insulin resistance playing you up. Hormones trigger our livers to dump in the event of lower glucose when fasting and between meals, and then the pancreas secretes insulin to push this glucose in the cells where it is needed, and keeps the glucose balance as it should be. In normal people, this keeps the cells happy and the glucose at normal levels, and the liver stops dumping. What happens with us is the secreted insulin can't push the glucose to the cells where it is needed due to insulin resistance, so the glucose stays in the blood stream a long time. The only other reason is when the pancreas isn't producing enough insulin in the first place. Intermittent fasting should help with the IR, so do keep doing it.
I also do 18/6 fasting, and I also have a coffee with cream almost as soon as I get up, and that keeps me low and flat all morning - but I suspect my insulin resistance has diminished sufficiently for any liver dumps to become insignificant. I only get them now after strenuous exercise. Probably because strenuous exercise is a rare shock to my system!!!!!!