depreciation cannot be exceed business basis

I purchased a hay trailer in 2010 for $5000. I sole the trailer in 2020 for $3500. The trailer was already depreciated and full amount deducted on section 179. When I entered this information in Turbo Tax, I get an error that the "depreciation cannot exceed business basis".  All of this information is correct, but somewhere Turbo Tax is seeing an error. I am not sure what to change to correct this error. Any ideas?

 

Thanks for your help