Module "factory" reset, state as from Digi

I have developed some application using NETOS. It it more or less functioning. Now I want to product some device for testers. My application consists of 3 file: image, backup and rom (bootloader). When I was trying to upload this files to development module which has running ftp server demo everything was working OK. When I was trying to upload all files to “brand new” module something went wrong, board was bricked and after few tries I manage to recover it. I want to investigate this issue, but I don’t have more “brand new” modules. How can I recover board firmware to state as from factory? On my board currently everything was changed.