Thank you for the details.
Very probably this protection is armed just in case the ESC is not fully initialized or received a bad signal.
The wrong signal will be there if the unit is very old (which will require modification).
If both of your unit are starting with serial number of 53- then they are produced very likely in the same batch
Unfortunately at the time they were produced we didn't know there will be ever such feature so until now it was not a problem.
But your units will very likely require to change a resistor, then everything will work.

Since we are testing completely each cable with CC Edge and it worked, the problem must be probably just in this.
In any way, we will try to get some of the older units to check if we will see same kind of protection.

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Spirit System developer

So after testing (we have created unit with same resistor on yours) we can confirm exactly same results.
The ESC does not initialize at all and we are getting low voltage alarm. The BEC output is 4.3V.

So fortunately now we know exactly where is the problem - both your units are from the same series where resistance was too high to make it work. At least we can fix it easily and quickly.

Now there is question if you can send the units to us? If you want to fly, you can send just one and then another.
For sure it will work then. Sorry for the troubles.

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Spirit System developer

ok Good that you were able to reproduce this problem.

You can do so in a bubble wrap (just units) or any other box to the address that is on the white Spirit box.
Important is to declare package value not higher than $25.
Then all will be OK.

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Spirit System developer

Thanks

Of course, you are welcome.

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Spirit System developer