WARNING

BoardConfigCommon.mk doesn't contain PARTITION_SIZE values, which have to be added manually in this directory: "device/lge/your-specific-lgg5-device/BoardConfig.mk"

Why should I do it manually?

Different LG G5 devices doesn't have the same PARTITION_SIZE values.

Instruction

Simply paste these lines in "device/lge/your-specific-lgg5-device/BoardConfig.mk" and fill them with the correct partition value.

BOARD_BOOTIMAGE_PARTITION_SIZE := *my_bootimage_partition_size*
BOARD_CACHEIMAGE_PARTITION_SIZE := 
BOARD_PERSISTIMAGE_PARTITION_SIZE := 
BOARD_RECOVERYIMAGE_PARTITION_SIZE := 
BOARD_SYSTEMIMAGE_PARTITION_SIZE := 
BOARD_USERDATAIMAGE_PARTITION_SIZE :=

How do I get the correct partition value?

Open your terminal (TWRP is fine) and enter:

blockdev --getsize64 /dev/block/bootdevice/by-name/*every_partition_you_need*