An extraction should smell and taste like what it was extracted from. I trust that isn't what the starting material smelled like, or we wouldn't be having this conversation.
Taste sensations are sometimes hard for two people to identify as the same sensation. I sometimes taste the corn in QWET done with white lightning corn squeezings, but not in ISO.
If it has dragged over more than one strain, I suspect the process, which could be residual ISO. You might try vacuum purging at -29.5" Hg and 115F, to observe what happens and if the flavor goes away.
Adding more water to the formula brings in other water soluble variables, which might taste like corn to you, so would stick with 99% ISO, which we can get at our local Safeway.
If you are using the same purging techniques for 91% as Oakley's 99%, you may possibly be leaving some water behind, along with what ever water solubles they dragged along.
starting materials are as follows
frozen bud.from my local dealer/friend/homie..usually fire..
frozen iso 91% from wallyworld..
frozen jars to pour in
frozen filters,lids,and everything that I may need in the end is frozen..
I ad about a 1/2 inch of iso over the levelness of crumbled up bud.
shake/stir for about 30 secs .wait for another 30 sec. then pour thru metal coffee filter then that goes into a double filter on top a mason jar..
I let it drain thru in the freezer
pour into pyrex tray and either air dry or low heat until dry.
most of the time I have a very nice golden or amber shatter but it always taste like corn aftertaste even if I use different brands of iso and buds..
I don't have a vacc. or a way to get one.. I am thinking of doing butane but at $10 a can for stak. vs $2.50 for a big bottle of iso..
I have tried different filters , different bud ,different iso. great non crackling ,popin dabs but CORN.