A quick note: An I2C device cannot hold a line high -- that's the default state. Since I2C is an open-drain bus, devices can either actively pull the line low or release it to the default state of high. According to the scope shots, it looks like a device is holding the SDA line low at the end of the transaction and the clock line at it's default state of high.
The Problem
You can see in the scope shot that the last byte sent is 0x3B, as expected. After that, there is one more clock pulse to allow the master to ACK, which it does by pulling the data line low for that clock pulse (the master can either ACK or NACK on the last byte, it doesn't matter). Then, a stop condition should be sent, which is when a rising edge on SDA occurs while SCL is high. This is all described in the INA233 datasheet:
Your scope shot looks correct until the very end, where the master ACKs (allowable according to footnote 3) but then does not send the stop bit seeing as the data line stays low.
Because some device is holding SDA low after the last byte, and no STOP condition was sent, this might be why the Beagle thinks that there was a third byte sent. It does detect the timeout (the "T" in the error column) but thinks that there's a partial byte as well, probably from the clock going high and then no stop condition so it looks like another byte coming.
That's a detailed look at what the problem is: something is preventing the data line from being released at the end of a transaction. So what could be causing this?
Speculation on the Cause
The fact that the bus remains locked up permanently until a reset hints to me that it's not the INA233 that's the problem -- it has a 28ms timeout specifically to prevent this type of issue. If the INA233 was the culprit, you'd expect to see this issue cause affect a single transaction, but not for the bus to permanently lock up. SDA should be released after 28ms if it was the fault of the INA233 and everything should go back to normal.
That means that I'd start looking at the master device, and particularly taking a careful look at how you turn on the brake motor (since that seems to be the instigator). Your supply voltages aren't noisy and same goes for the data lines, so EMI probably isn't causing the failure. And if the motor itself was the issue, I'd expect to see the bus fail exactly when the motor turns on, not at the last bit of a packet, when everything had been working perfectly fine while the motor was running before.
So how about looking at how you turn on the motor from a firmware perspective? I'd take a look at any state changes when the motor turns on that might somehow affect how the I2C code does it's thing. Or perhaps it's an accidental forever loop on the master after receiving the last byte, therefore never sending the STOP condition. The motor itself feels like a red herring, which could be verified by disconnecting the motor from power and trying again.
I wish I could give a more solid answer, but I hope that this is able to point you towards something more specific to debug. I know that this is a bit of a typical hardware answer, calling it a software problem because the hardware is never the problem, but based on what's given here, I do feel that examining the master code is likely a good move. Best of luck!
