I think you are right. Yeah, lets hope it is just reseted and not buggy…
I just checked the latest achievements of all trophies and there are no trophies (that have a counter) achieved after the 2nd / early 3rd of September. And yeah, the latest game update was released on the 3rd so there must be a connection.
Please let us know if your friend can unlock his last trophy. Then we at least know that there is no bug