Certain monster variants that fly in (ie. osprix), emerge from the ground (ie. beetles), or blink/teleport/stealth (ie. nagasa) aren’t targeted by totems if the totems were placed before they appear.
This also occurs with all monsters, regardless of type, in the Arena and Lagon’s tentacle phase; totems won’t attack subsequent waves of monsters. Tested it with storm/thorn totems, so might not be the case with other totem variants.
Only when the totems are resummoned, are the spawned enemies targeted by them.
Related issue: Storm totem does not attack Lagon, after the tentacle phase in the “Ending the Storm” monolith boss fight. Tested it with Thorn totems, and they work normally, so it seems like an issue with just Storm totem.