I just found that a lot of my models are now showing as the standard digital license when I originally released them with the share-alike, no commercial. I did not make these changes to the licence type, and I am 100% sure I had them marked as CC-BY-NC-SA.
Why would these be updated at all, and if something triggered this, why wasn’t there a notification?
Did you perhaps enter them into the exclusive program? That automatically puts them on SDFL. That is the only option for being in the exclusive program. Hopefully you can find out what happened! 
Are you sure?
I agree with @3DJL that would make the most sense, except NONE of your models are marked as exclusive.
The other big issue is, that I checked half of your models they are all CC-BY-NC-SA exactly as you said you wanted.
I have not found any Standard Digitial Licence models.
Granted I have only looked at half of your models, but you said a lot of them, I figured I would have spotted one by now.
Please share any links to the models affected.
I did not enter them into the exclusive program, and I am 100% that they were not marked as standard license.
I checked and updated every model back to the correct license type after I figured it out. It was about 12 of my 29 posted models.
You should create a ticket and provide a few of the affected model links for MW to investigate.
You do not want it to happen again.
Then report back so others can watch out.