I have a maytech vesc 4.12 from eskating.eu that i have been using for a single drive,( 12s lipo 168kv sk3) without problems for about a year now. But now i am uppgrading to dual. I got another maytech 4.12 and another motor, tb trucks motormounts etc. I went to uppgrade the firmware on the vesc’s to 3.4 using vesctool and on the new previously unused one, everything went fine, uppgraded firmware did motor-detection and everything else.
But when I try to uppgrade the firmware on the vesc i have been using for a while (previously 2.18) the uppload seems to go ok, but a the very last second it disconnects saying “No such directory exists” or something similar. After that i cant connect to the vesc again until I turn it of and on again, at wich point it connects and still shows the old 2.18 firmware. And with the old fimware i cant change any settings in vesctool wich is a problem since i plan to connect the vesc’s to eachother via canbus.
I have tried uppgrading the firmware both using vesctool and ackmaniacks vesctool but the same thing happens. If i start up the old bldc tool i can make changes, run motor detection and such but I’m scared to connect the vesc’s on canbus when they are on different firmwares.
Does anyone know why this is happening or what I could do to solve it? I guess i could try to find 2.18 fw for the other vesc and downgrade it using bldc-tool but i would much rather run them both on 3.4 fw. Is it okay to have two vesc’s on different firmwares?
i’'ve updated my vesc’s using ackmaniac esc tool, from Fw 2.54 to 3.10 even thoug it’s the latest updat in Fw to my knoulge, but found out fw 3.10 it wont work with controller that i got for dual can-bus connection 
tried few times changing thes vese fw to 2.18 still can.