Spider adds from Essence were running around although it wasn't activated yet (Bug #2.248.752.684)

This was a strange one. We saw the Essence but then those spiders appeared and we first thought they were regular ones, but they started glitching and couldn't be damaged or killed, only deal damage.
There also was no name showing up, when hovering the mouse pointer over then.

Finally, we opened the Essence after which everything went back to normal, except that the adds came running from below instead of appearing from where they normally do.

Video: https://youtu.be/HB5q3UuH_qM

I happened again, this time in the "Valley of the Titans", but this time they didn't attack.



If you walk away from the essence, the adds follow you and then stay there:



They block your way, but have no name tag.

Bug# 632.218.327

Had idenical bug a few weeks before yours. See my thread: https://www.pathofexile.com/forum/view-thread/3654841