Boss death not giving credit

[Shiloh]

We offed the lvl 55 boss and it didn't register, anyone else having this problem?

[Krayt]

We killed one and it didn't show but after killing the second it corrected itself

[_Mas_]

No problems so far for us...

[Artorius]

We have taken down three in a row at level 50 no problems at all. Actually prizes much better all rare or epic through entire guild.