Just updated my 2017 Legacy (no Nav). Here is my before & after. Thankfully update #2 took on the first try it appears
I kept the car running for each update. I didn't use a battery charger. I made sure the headlights, interior lights, etc. were fully OFF though. After the reboot & wait step, I just turned the key to ACC (didn't start the engine again).
Nor OU9606 > OU9510
eSD OU9606 > OU9510
POWER 02.1026 > 02.1026
CAN 14.0015 > 14.0015
POWER BOOT 02.1117 > 02.1117
POWER VCL 02.0103 > 02.0103
Backup DB OU9606 > OU9510
BUSBF4_3.A 03 > 03
BUSBD4_4.A 03 > 03
Vcl_Para 09.49 > 09.49