The allay will get stuck on blocks such as glass, fences, and stairs. Those are the only areas and blocks in which I am aware of, however, the stares were the most recently discovered bug, so I don't doubt that there are other block trap bugs in which I am unaware of.

Here are a few screenshots to help give a visual of what's going on:

Image 2: allays stuck to glass
Image 3: Allays stuck to fences (hard to make out, but it's nighttime)
Image 2: Allays stuck to stairs