You may have already done this, but I would contact another outside agent to ask for comp's. The answer may come in differently.
Another option is to find an Appraiser that will do a "Desktop" appraisal. In our area it's about $100.
It won' be as in depth as one done by a lender, but the results are basically the same. We've had them literally come in for the exact same appraised value as the lender. Again, this is a Licensed Appraiser that
performs these. It's definitely worth the $100 & we actually do them quite often before we open escrow so our chances of falling out over the lender's appraisal is basically eliminated.