Having never  filed a business casualty loss for a client and not wanting to beat a dead horse I do have a question.

By definition, adjusted basis would include original cost plus improvements, minus depreciation and Casualty losses Plus any reimbursement and the net should be casualty loss or gain.

You may be filing additional forms or taking extra steps that are needed.

Please note, this is from the point of view of a preparer not experienced with form 4684.