about 4 out of 7 times, yes i tested it that much, i conjure a familiar i turn invisible and my magika replenishes. Awesome, yes, but it does that instead of conjuring the creature. Has anyone else crossed this bug before?

It is caused from having absorb spell effects active. Conjuration is seen as cast on self. So if you have the Guardian Stone that grants 50% spell absorb, then you will only be able to cast it 50% of the time. When the Familiar does not appear and you regain the Magicka, is caused from the absorb effect.

Your character vanishing for a second is a buggy side effect of this, This is a known issue and I am not sure if it has been addressed and corrected in the latest patch.

Oh, okay. Thank you! I am a breton with the atronoch stone. Probably why it rarely works hahaha

That doesn't sound as annoying as my flaming familiars that decides to heat seek me !

That will do it. And you are more than welcome.