I use the Conjuration skill to reanimate some of my kills as followers. I have noted that even though I can only have two reanimated followers that in my active effects list I show this spell as active five times. I have had the effect of having one of my thralls falling dead when leaving an interior cell and also had thralls i lost long ago suddenly come running up to me. Does this skill get buggy when my raised dead get lost from me while I am traveling allowing me to have more when outside of the cell they were lost in or is there something else going on?

Yes, Raising the Dead is one of the buggiest things in Skyrim sadly

I've had buggy conjuration in vanilla Skyrim but problem solved with USKP if your on PC.

1. Do You use a Bashed Patch?

If You answered Yes, have You changed the Max Summons?

When I last played a Necromancer, the Twin Souls Perk would override the Max Summons of the Bashed Patch, but I could have Five Thralls before taking the Perk.

I still will get a Glitched Durnheviir that does not fly, but I can use a Familiar to cancel the Glitch Durnheviir. Familiars are also good for testing the amount of Summons a character can have, and can be used to disable Dead Thralls for storage in a Player Home.