[Moto G5 Plus Questions & Answers] MrsMotz:
OK, I tried the first bunch of commands. This is the result I got:

C:\ADB>fastboot devices

6be2e0bf fastboot

C:\ADB>fastboot oem fb_mode_set

...

FAILED (remote failure)

finished. total time: 0.013s

C:\ADB>

C:\ADB>fastboot flash logo logo.bin

target reported max download size of 534773760 bytes

sending 'logo' (2186 KB)...

OKAY [ 0.084s]

writing 'logo'...

(bootloader) Failed to erase partition

(bootloader) Failed to flash partition logo

FAILED (remote failure)

finished. total time: 0.107s

C:\ADB>fastboot flash boot boot.img

target reported max download size of 534773760 bytes

sending 'boot' (16384 KB)...

OKAY [ 0.603s]

writing 'boot'...

(bootloader) Image boot failed validation

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 0.807s

C:\ADB>fastboot flash recovery recovery.img

target reported max download size of 534773760 bytes

sending 'recovery' (20580 KB)...

OKAY [ 0.738s]

writing 'recovery'...

(bootloader) Image recovery failed validation

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 0.981s

C:\ADB>fastboot flash dsp adspso.bin

target reported max download size of 534773760 bytes

sending 'dsp' (16384 KB)...

OKAY [ 0.584s]

writing 'dsp'...

(bootloader) Failed to erase partition

(bootloader) Failed to flash partition dsp

FAILED (remote failure)

finished. total time: 0.606s

C:\ADB>fastboot flash oem oem.img

target reported max download size of 534773760 bytes

sending 'oem' (104608 KB)...

OKAY [ 3.643s]

writing 'oem'...

(bootloader) Image o failed validation

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 3.714s

C:\ADB>fastboot flash system system.img_sparsechunk.0

target reported max download size of 534773760 bytes

sending 'system' (258396 KB)...

OKAY [ 8.946s]

writing 'system'...

(bootloader) Image s failed validation

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 9.017s

C:\ADB>fastboot flash system system.img_sparsechunk.1

target reported max download size of 534773760 bytes

sending 'system' (256514 KB)...

OKAY [ 8.872s]

writing 'system'...

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 8.896s

C:\ADB>fastboot flash system system.img_sparsechunk.2

target reported max download size of 534773760 bytes

sending 'system' (246302 KB)...

OKAY [ 8.489s]

writing 'system'...

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 8.530s

C:\ADB>fastboot flash system system.img_sparsechunk.3

target reported max download size of 534773760 bytes

sending 'system' (262141 KB)...

OKAY [ 9.057s]

writing 'system'...

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 9.149s

C:\ADB>fastboot flash system system.img_sparsechunk.4

target reported max download size of 534773760 bytes

sending 'system' (262141 KB)...

OKAY [ 9.063s]

writing 'system'...

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 9.092s

C:\ADB>fastboot flash system system.img_sparsechunk.5

target reported max download size of 534773760 bytes

sending 'system' (262141 KB)...

OKAY [ 9.070s]

writing 'system'...

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 9.096s

C:\ADB>fastboot flash system system.img_sparsechunk.6

target reported max download size of 534773760 bytes

sending 'system' (250531 KB)...

OKAY [ 8.684s]

writing 'system'...

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 8.725s

C:\ADB>fastboot flash system system.img_sparsechunk.7

target reported max download size of 534773760 bytes

sending 'system' (262059 KB)...

OKAY [ 9.034s]

writing 'system'...

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 9.073s

C:\ADB>fastboot flash system system.img_sparsechunk.8

target reported max download size of 534773760 bytes

sending 'system' (254142 KB)...

OKAY [ 8.763s]

writing 'system'...

(bootloader) Invalid signed image

(bootloader) Preflash validation failed

FAILED (remote failure)

finished. total time: 8.796s

C:\ADB>fastboot flash modem NON-HLOS.bin

target reported max download size of 534773760 bytes

sending 'modem' (71921 KB)...

OKAY [ 2.495s]

writing 'modem'...

(bootloader) Failed to erase partition

FAILED (remote failure)

finished. total time: 2.522s

C:\ADB>fastboot erase modemst1

erasing 'modemst1'...

(bootloader) Failed to erase partition

FAILED (remote failure)

finished. total time: 0.019s

C:\ADB>fastboot erase modemst2

erasing 'modemst2'...

(bootloader) Failed to erase partition

FAILED (remote failure)

finished. total time: 0.034s

C:\ADB>fastboot flash fsg fsg.mbn

target reported max download size of 534773760 bytes

sending 'fsg' (3012 KB)...

OKAY [ 0.126s]

writing 'fsg'...

(bootloader) Failed to erase partition

(bootloader) Failed to flash partition fsg

FAILED (remote failure)

finished. total time: 0.146s

C:\ADB>fastboot erase cache

erasing 'cache'...

(bootloader) Failed to erase partition

FAILED (remote failure)

finished. total time: 0.034s

C:\ADB>

C:\ADB>fastboot erase clogo

erasing 'clogo'...

(bootloader) Permission denied

FAILED (remote failure)

finished. total time: 0.018s

C:\ADB>fastboot oem fb_mode_clear

...

FAILED (remote failure)

finished. total time: 0.021s

C:\ADB>fastboot reboot