Hi, this has happened twice to me now.
Upon speaking to the NPC to enter the BCA, instead, your NPC can get frozen in place instead of being transported to the Bug Catching Area. The client won't let you send messages, or check inventory. Curiously you can still open the pokedex and your friends list, but your character remains frozen. The only fix is to restart the client., and that teleports you to the BCA finishing room, where you are obviously disqualified.
Instead of a usual 24 hour cooldown, you are left with a 16 hour cooldown.
It should be noted that both times I only had 1 pokemon in my party when selecting the poke i choose to take.
Hope his helps with any other people who have experienced this.