I had this same issue. Then I studied the LUA upload tool (NodeMCU-PyFlasher-1.0.1), Then I tried all diff perms and combs until I got a working LUA firmware flashed sucessfully. Then I mimicked those params to esptool.py .... This is same as @Phando (but running with esptool.py 1.3).
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Just an update:
I had this same issue. Then I studied the LUA upload tool (NodeMCU-PyFlasher-1.0.1), Then I tried all diff perms and combs until I got a working LUA firmware flashed sucessfully. Then I mimicked those params to esptool.py .... This is same as @Phando (but running with esptool.py 1.3).