Quad Cοpter 4.5.1 fail with crash LOG Review Help will be appreciated

Apparently when it rains is pours and for this i would like to get an extra opinion.
670 Quad, 4014 330kv T-motors, MF1608, T-Motor F66 ESC running Dshot and ESC telemetry, Cube Orange, Holybro UM982 configured for GPS YAW with Fallback compass, CUAV C-RTK2 mostly for the camera tags. Running on 6S.
Max Vibes only on X at 15 and mean vibes between 3.8 and 6.8max depending the Axis.
I did atleast 3-4 flight before verifying that it works on, its stable enough to autotune and configure Harmonic Notch frequencies with ESC telemetry.
After all than and another 10min flight i decided to run autotune and here is the issue.
I would not like for now to give any direction to anyone that decided to review the log for what i have found, but i will be looking for ideas on why did motor 2 and 3 on an all in one ESC show at the moment of all failures that their voltage dropped to ZERO, while the ESC 1 and 4 had proper voltage.

Hi @MerkaTony,

I haven’t investigated too thoroughly but it looks like a motor failure of Motor2. This is a QuadX frame so that is the back left motor.

This has the classic signs of a motor failure:

  1. The bad motor (Motor2, back-left, shown in red) goes to maximum and the opposite motor (Motor 1, front-right, shown in blue) goes to minimum.
  2. The vehicle rotates towards the failed motor. In the pic below we see that the actual roll (in green) becomes negative meaning it rolls left. The actual pitch (shown in yellow-ish orange) becomes positive meaning it pitches back. So left-back towards the failed motor.

@rmackay9 thank you for verifying that. At the moment all motor tests show that its not the motor that failed but the arm of the motor that caused the issue. My biggest question in case you have ever seen this before is how 2 out of 4 esc on an 4in1 esc drop from their voltage to Zero. Have you ever seen anything like this before?

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Hi @MerkaTony,

It does look a bit like 2 of 4 have failed which I’ve never seen before. I don’t personally use 4-in-1 ESCs although they seem like great space savers.

Check your solder points. I’ve had a cable come completely loose, but it stayed in place by pure luck. So the motor would work just fine… until it moved a little and suddenly the motor cut out.

@Oli1 , this is a 4in1 esc and V seems to drop to zero on 2 out of 4 at the same moment.
Motor Solder Joints got checked a few times before and also now that we took all motors out have have them on a thrust bench testing to see if they will fail.
i have to check if the esc telemetry gives V value with out motors, because i recall it did.
This is the point i find wierd. And i have also Tmotor Looking into it.

Oh, right, 4in1. Weird indeed.
ESC.Temp cuts out to zero a couple of times. I’m by no means an expert but I’d assume this points to some kind of connection issue between ESC and FC. Or a faulty ESC.

@Oli1 another interesting find on the 4in1 esc is the voltages of 1 and 4 ESC at the moment 2 and 3 went 0v.
Those two ESCs spiked to 28+v which makes no sense on a 6S battery on a not completely tuned PM that started the main battery log at almost 24.5v instead of 25.2.
Along side the Volts you can also see that the Temp goes to 0 and with a since Telem Cable for all (esc gives one Telem cable as output) connecting to Telem2, really makes no sense why they got disconnected(?) unless the ESC has an issue.
I have contacted the people at Tmotor and im waiting to see how this goes.