That's not a new bug.
It was from the old days, when we had both versions T11 2014/15 and T11 2016/17.
All of sudden, one day the player you had for nego earned skills.
@ RClub has a factory for nego players (lol) so it's happening very often for his players.

p.s. I also wonder if it was a bug or devs made this on purpose to destroy negotiation players you keep for a long time.