bug at platform and party instance bug

i was in a party and killed the fire boss in act 3. Alva was called to investigate the platform, i went off of it to get something and wasnt able to rejoin once the alva animation started and was left behind and had to rekill the boss.

Also, in the viper boss in that same party we all died and i respawned. when they respawned, they were in a completely different instance and went on for the kill without me.

very frustrating.