Interesting. Much like the OP, and some of the rest of you, I received my car in mid December. I have had no issues with my UMC gen 2. I was having some other issues with my vehicle, and they sent out a ranger to update my firmware today and take a look, which I thought odd since the firmware can be deployed remotely.
Anyway, once in site, he wanted to see my UMC. I wondered what this might have to do with my problem, and he said my VIN was flagged as receiving a possibly bad UMC and to replace it. He didn't know why, or what issues it may have caused, only that the serial number fell within a range of those that were supposed to be replaced.
Strangely I had my car in for service in April, and this was not mentioned. So it seems they may have found a defect in the early batches of the gen 2 UMC and are replacing them.