Instruction:
Boot the switch with firmware version 1.2.71.203 
Upload jump code ECS4100_Jump_V1.08.1.203.bix to the switch
Boot the switch with jump code
Delete Firmware V1.2.71.203
Upload newer firmware V1.2.73.203
Boot the switch with firmware V1.2.73.203
Delete Jump code.
 

Caution: ECS4100_Jump_V1.08.1.203.bix does NOT support ECS4100-12PH.