The below statement jumps out at me:
There were some years between 2004 and present where I lived in the unit and it was not depreciated as rental.
Are you saying you have some years where it was still classified as a rental with less than 100% business use for each of those years? Or are you saying there are years where you lived in it for personal use for the entire tax year, and did "NOT" report it on SCH E since it would not have been a rental for even one day in that tax year?
I ask, because when you have tax years with varying percentage of business use, or varying percentages of personal use, that will change the allowed depreciation for that tax year. That can "and will" throw things off. In my testing with the TTX program a few years ago (maybe 2 years ago) the program flat out was not able to handle it correctly.
