I had the same issue with a SF302-08.
I did following:
1. Boot the device
2. Wait for the test mode
3. Press N (Not documented option)
Following menu appears:
# '0' - Turn on Burn-In flag ; '1' - Config Burn-In parameters
# '2' - Show Burn-In information ; '3' - Show flash information
# '4' - Turn off Burn-In flag
4. Choose Option '1' - Config Burn-In parameters
Following appears:
# Set Power cycle ...
# Cycle range: 0001 ~ 9999
# Input Power cycle:
5. Power cycle the device without enter a number
6. The device boots with the Cisco image
Makes no sense but it works in my case.