While soloing Chaos 1 Trials, I was assigned to Forgotten Ruins, and had a curious incident occur on Wave-5.  An Ogre got stuck inside his spawn point inside Mountain Path, and proceeded to be a combat nonentity for the rest of the fight.  He was stuck so far back that normally, I couldn't have killed him, were it not for my Abyss Lord's Dark Syphon and Huntress's Piercing Shot, both of which could penetrate the spawn barrier and deal damage to the stuck Ogre.

Not entirely sure if this is reliably reproducible, as it requires an Ogre to come down a very specific lane and possibly be pushed off-path and into a collision issue by other mobs shouldering past.  Other Ogres previously encountered on that lane managed to get through the spawn and attack my defenses with no issues.

Nonetheless, I did get a screenshot!