Sometimes, the burnt on 'crude', is so carbonized that the lye can't get under it to remove it. In cases like this (even after months in the lye bath), I would score/scratch the carbonized stuff and then place it back in the lye (in your case the oven cleaner and bag). This will also help.
However, it looks like this skillet is going to look like new, it just takes some time/patience. You are getting there. As others have stated, watch out for cast ironitis, it is addicting.