The DSONEi is same that DSONEi Mini but with a Firmware Writer in extra.
I updated my DSONEi (v1.4.1) with the DSONEi Mini Firmware v.1.4.2 without any problem.
Today by curiosity I reupdated my DSONEi (v1.4.2) with the Firmware Writer & the DSONEi FW v.1.4.2 without any problem.
Maybe Your problem is a contact problem. Clean the pins and Retry with the Firmware Writer. Good luck.