When I hit 64th level expeditions, I noticed anytime I go to the third tier now and kill the boss I instantly get kicked from the expedition, and a fail message. I first thought we were trading deaths, but upon further testing it results regardless if I am at full health with respawns available. This happened on the Lambach also, but I got around it by letting a friend get the final hit. That friend no longer plays and I am not going to want to invite someone in just to get past this every time. I realize as I have not read anyone with this problem it might be "lag" or a character bug unique to my account. Even knowing it is most likely a low priority issue, by posting maybe eventually it will get looked at because I am now stuck in progress until it does.

Here is the bug:

Summary: Any tier 3 64+ Expedition boss on my character Koros can not be killed, as the kill results in an instant lobby close and failure notice.

Steps to Reproduce:

1) Create a character and finish story mode (My Character is 63, Fire Ailment build, Dagger primary Catalyst offhand)
2) Skills I am using: Plagueburst, anamoly, solar fall, Bulwark of Dawn, havoc orb as rage dump
3) Finish Expeditions until you reach level 64.
4) Start and complete first 2 tiers then attempt to finish 3rd tier boss

Results: Regardless of Boss Arch-type, when killing the boss instead of dropping loot, as the death animation starts the lobby closes and character is teleported back to the vendor lobby with a message that they have failed the expedition.

Expected Results: Death Animation should finish, loot should drop and player should be rewarded with progress on the expedition selection screen.

NOTES: This happens irregardless of modifiers. I have tested multiple times over the last two days with different passive tree (maintaining an elemental ailment build because of gear and gem selection) active skills and modifiers. I have played mandates with no issue, I can clear any level prior to 64, and I can clear and kill any boss prior to tier 3 of level 64. The issue only has presented itself on the one story mode Boss as described above, and the third tier boss of expedition level 64. Since I can not kill this boss, I have not been able to test higher tier expeditions to see if the same result is present.