sounds like the usual anti spark issue or similar, also there was a drv fault triggerd in the logging. That does not mean there is a DRV Problem for sure. After fixing the Power issue I would check the drv/powerstage area and try if you can trigger the issue on the bench again 
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They are connected to a momentary switch. I’ve tested the MOM pins for continuity and it’s functioning correctly.
Fair point. Metr was reporting 7v (while the Unity was still on). When I checked the BMS app, it reported ~50v. I concede that when I had the opportunity to physically measure voltages across the system, there was nothing that was reporting 7v. I’m not skilled/knowledgable enough to take measurements on the Unity PCB beyond the PCB’s main power terminals.
Yes, the Unity itself, measured here:
Granted. Your assumption was correct: the board was frustratingly stationary.
If by ‘power issue’ you’re referring to the likelihood of a disconnection along the power supply, I honestly think that we can rule that out. I checked and double-checked after @Deodand’s earlier observation and I did so again yesterday. Solder joints are solid. XT90’s are so tight I need tools to unplug them. I can accept that the BMS is a potential point of failure here but my gut tells me that the issue is with the Unity.
Could you share a few pointers on how I can, “check the drv/powerstage area” please, @seaborder?
I’ve had other feedback by DM, saying, “It sounds like only the precharge circuit is broken”, as well. Can it be coincidence that I’ve blown two Unity’s a/s systems? I mean, could I have fucked up some aspect of the build or configuration that makes this more likely to happen? What factors determine a/s health (assuming it leaves the factory healthy)?
Thanks everybody for working with me on this. I really appreciate the support. You guys rock 
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It is difficult to see… is this blown? It’s the charge pump for the transistors doing the precharge.
I guess you have zero volts across the big capacitors when you try to power up?..and that would be why its dead stationary but alive when being powered backwards during regeneration from the motors.
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Hey guys, I have been trying my best looking through the forum for solutions to my focbox unity but eventually gave up and bought another one. This is ultimately my third purchase of the unity. Anyways the issue always happened when one of the pins on my vx1 receiver would short out I am not entirely sure which pins specifically, but when I try to turn on the unity it powers off in seconds. I saw that this could be a bootloader problem that would just require a reflash with a St-Link v2, but that has been no luck either (I tried finding the reset pin, and double-checked the wiring on the St-link’s pcb and orientation of the jumper cables on the unity. I checked with my multimeter and the unity only supplies power to 5v and not 3.3v does that mean the MCU is messed up permanently? This is my third time shorting something out with the vx1 receiver and I wish there was a protection circuit to prevent this from messing up my unity.
No, I don’t think so. Everything looks kosher. The application of the conformal coating is definitely questionable but nothing looks blown.
…and zero volts across the caps, yes. To be clear, the unit is totally unresponsive if I try to power it up.
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Your picture still does not convince me… it still looks like a hole… coating burnt off 
You might be right. Its just that the unities I have reworked have had a hole in that component on that same place
Perhaps scraping the coating off will reveal the dirty truth?
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Well I’ll be damned.
You’ve got a hawkeye there, @Fatglottis.
What’s the fix? Replace it or rip out the a/s?
And guys, I really need to know: is this just a recurring product issue or am I over-driving it somehow and causing this to happen?
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loopkey
or another AS 
Interesting… My blown unity has a divot there but no hole blown through it.
You got some fine peepers @Fatglottis 
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In this case I suggest removing it. It’s just sad if it breaks again, also I don’t know about the status of other components in this circuit now.
Yes that divot is there as a marker to show the leg orientation so that the IC is not accidentally rotated 180deg.
My laser vision tells me your unity has more severe issues 
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A blind person would be able to diagnose based on smell alone.
On the bench under no load too. I think I got home just in time to avoid a bad situation.
Good warning for all esk8 folks:
If your shit is acting weird, go home. Your body knows your board and when something is different.
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Ima just chip in here. Im soon completing my board with a Unity that has been laying at my house from one of the last batches from enertion. Is there any precautions i can take to minimise the risk for say, the builtin precharge? Im going to be usin a lookkey out of an XT90S, should i bridge those 2 pins of the momentary switch and simply remove that switch?
Yes, if u r using a loopkey u can bridge the MOM pins and never worry about it
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Anyone wanna stick their neck out here and share their opinion?
It’s possible you have a cold solder joint in your battery or xt90 that intermittent if you loose power during regen it will blow the tits off a unity/tenka. They are also prone to self destruct of the 3v.curcuit requiring new regulator, MCU, leds ECT…I doubt it’s your config. Maybe lower your regen in future. Although if the above were true it would not have helped. I would change to a makerx DV6 ESC and loopkey. Way more robust.
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Just to loop back on this for completeness, @Fatglottis kindly bypassed the Unity’s onboard a/s for me and so far ever since she’s been running like a dream. If you experience similar related issues, and assuming he’s willing, I’d recommend working with Simon to get yours fixed too.
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Any idea why my Unity won’t detect my Maytech temperature sensors please? Comes up false for both. Hall sensors detected fine and motors running well. Unity running on VESC firmware. Just no temp reading…
What FW version on the unity?