if the butane sat in the oil for awhile it will not be able to purge the taste out. i have had this issue as well and depending on the heat you repurged at it could have effected the taste as well.
Making BHO is a science and i have yet to get the same results twice because i refuse to make it the same way ever. i change a variable everytime to see possible results and try and get the cleanest form of BHO possible.
to answer your question short and simple so i dont get into details here, the best way to "clean" bho (best meaning cheapest and safest) would be a Food Dehydrator. a simple cheap one from a thrift store will be more then what you need heat wise. throw it on the very top wrack with the vents all opened up and let it sit there for as many hrs as you want. it should never get to hot to cook the terpenes out and at the same time will speed up the purge of butane that can self purge its self at room temperature. (no whipping or babysitting needed with a food dehydrator)
place on parchment paper, fold it up, place on top, open vents, go watch some movies or walk the ridge line.
Will also add a pic of my honey comb i made couple days ago later today.
