Moto G2 (Titan): "fastboot flash recovery" won't work. my Basic Plan, is to install the latest Version of LineageOS 14.01 via TWRP 2.8.0.1. This failed with an error "unknown command [log]". Next Idea: update TWRP to latest Version 3.1 and try again. So i tried to Flash the Recovery Partition via: "fastboot flash recovery twrp-version-titan.img" (during the Process i tried different Versions like 2.8.6 and 3.1) and fastboot responded: 

    target reported max download size of 536870912 bytes
    sending 'recovery' (8724 KB)...
    OKAY [  0.296s]
    writing 'recovery'...
    OKAY [  0.204s]
    finished. total time: 0.500s


The messages on the Display seem to be ok (no error Messages) and I try to boot in Recovery Mode by choosing "Recovery" in Fastboot Mode. This works, except, that the installed Version stays the old TWRP 2.8.0.1 (I installed it some years ago).
So i tried to boot TRWP directly via: "fastboot -c "lge.kcal=0|0|0|x" boot Downloads/twrp-3.1.0-0-titan.img", (worked) and install a new Version from SD Card. This failed, because TWRP couldn't mount anything. 

During the whole Progress of try and error I messed something really up, because it won't even boot Android anymore. Flashing a stock Rom failed too. 

Has anybody an idea, how to "force" an recovery update? 

Sidenotes:


i'm working a mac
Android Studio is installed and updated incl. SDK Tools
i googled a lot
sorry for my english
Check the below link. This might help you.

https://forum.xda-developers.com/zuk-z1/development/win-zuk-z1-toolkit-0-1-alpha-t3235964

Though the solution mentioned is for Lenovo Zuk Z1 mobile phone. The process of doing it might help you solve your problem.