I have gotten this too. Usually when it's warmer and Humid out. I load too much and the draft drops off. Less load and inducer running longer and no problems here.So far I am not sure the liner has made that much of a difference other then an added safety factor.
With the stove in "idle" mode, over time, the inner flue temperature still goes down to ~100 - 150 degrees. Perhaps this will be normal and perhaps the liner just helps recover the flue temperature faster?
Using my Mark ii 25 manometer, the draft prior to installing the SS liner measured .08. Now readings jump between .08 to 1.04. Will need to reach out to HY-C to inquire about installing a draft regulator as the manual states one might be required, however HY-C support stated the manual is still being update.
Last, not sure why, but with this stove, the house has a much stronger camp fire/wood stove smell. Could also be that new stove burn off still. The smell kind of gives you a slight headache.