The necromancer PC travels all across the country with his favourite skeleton. It was animated via Animate Dead a long time ago and the necromancer kept casting it every day in order to retain control over the skeleton. But now, the necromancer has to take care of some business in Waterdeep. Meetings with nobles, appointments with tradespeople, stuff like that. He doesn’t want to bring his skeleton into the city, because this would raise some eyebrows (and potentially some weapons). On the other hand, he doesn’t want to leave the skeleton outside. Due to time pressure, he wouldn’t be able to visit his skeleton every day. Therefore, it would break free from his control and probably leave.
Can the necromancer dismantle his skeleton servant? Would this de-animate the skeleton? Could he put the bones into his Bag of Holding and later reanimate it after his business trip? (As was discussed in the comments, this particular bag of holding is not big enough to fit an entire skeleton, just its bones). This skeleton is near and dear to the necromancer’s heart and he doesn’t want to lose it.