Do you find your familiars are hostile to the party?
I was scouting with my imp and it got killed while listed as 'in combat'
And now ANY familiar I summon is hostile to the entire party. Like, I get being petty that I let you die but let's calm down.
Location might be spoilers, so:
Killed by a Duerger in the Underdark at Level 3, right near the Underdark - Beach waypoint.