My problem is resolved with an $80 steering sensor cable (P/N 34526771776).

The general progression of events:
Repairs to front left wheel assembly several months back for issues with carrier and hub.
Shortly after repairs, ABS/DSC/AWD warnings appeared randomly

After initial research in these forums, it was suggested could be weak battery. Considering mine was original from the July 2008 manufacture date, I went ahead and got a Duralast from Autozone. That ounce of prevention was likely prudent now that it's getting cold again in my area.

Indicators came back on, but turned out battery wasn't fully charged. Took it back to AutoZone and they juiced it up.

Indicators came back on. Took it on a few long rides to insure battery was given a fair break in/charge up, but indicators went off for a time and then came back.

Checked code reader and found 'steering angle sensor' fault and learned that I had to do the full left-right steering wheel movement to calibrate the steering sensor after battery replacement and registration with the car.

Indicators came back, intermittently. Sometimes after days of nothing. Sometimes immediately. I had thought maybe it was related to leaving the car inactive for a few days at a time.

Then a new fault came on showing a problem with the speed sensor and I read some other forum posts about it. As it turns out, that part was replaced as part of my front left wheel assembly work I mentioned at the start of this post. I also provided the parts to the mechanic, including a non-OEM speed sensor for $25 instead of an OEM which some dealers were selling on eBay for $80+ (new). My local dealer wanted $150!

So now with this new fault, I decided to just buy a new OEM sensor from Cleveland BMW on eBay. The replacement was the easiest work I've ever done on the car. The non-OEM sensor that I removed (which was only 2 months old) may not have been firmly plugged into the feed cable in the mini junction box in the wheel well. It seemed to come unplugged too easily, and I had to really firmly plug the new one into the socket to get it to snap into the connector.

In the past weeks, when I would start the car the indicators would be off. All I would have to do is turn the wheel to the left to almost full rotation and they would come on without fail. Or if I started to drive and make a left turn they would often come on.

So...it was possibly a bad non-OEM sensor or it was possibly that it was simply not plugged in firmly enough. I'm not going to take the wheel off and try it again. All works now and I'm happy to be done with this plaguing problem.

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2017 X4 xDrive28i