Moss Hornets pass through objects when attacking, but not when returning to the nest. This can get them stuck on walls/pillars/trees/etc until they get a new attack target.
Actually, it's a bit worse than I thought. It seems they can get stuck even when trying to attack, and sometimes even get stuck a long way away from the nest.
Here's a vid: https://www.youtube.com/watch?v=08Lyf1yZ-pY
Here's a screenshot where a hornet was stuck in a different lane, trying to return to the nest by the bottom crystal:
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