Instruction:

Copy 7125a.bin and 7125b.bin in the folder where the current 7125.bin is.
Back up the existing bin file.
Rename 7125a.bin to 7125.bin.
Try the system. 
If the sonar does not ping. 
Rename 7125.bin to 7125a.bin
Rename 7125b.bin to 7125.bin
Try the system
