1.8/spigot bugs
I've encountered 2 bugs so far, that with some searching, might be attributed to Spigot. (at least, I've found bug reports on the Spigot forum from other people on other servers)
1. A newly made map item seemed to be created at the 1:8 level, and does not align itself to a grid.
Spigot bug report: http://www.spigotmc.org/threads/maps-zoomed-out-level-3-4-1-8-scaling.38626/
What it's supposed to do: http://minecraft.gamepedia.com/Empty_Map#Zoom_out
2. Sometimes items dropped by mobs get ejected through blocks much farther than they're supposed to go, outside any expected collection area for a farm.
Spigot bug report: http://www.spigotmc.org/threads/mob-drops-ejecting-outside-expected-collection-areas.38859/
I don't have a fix or anything but if you guys come across these or others, please share.
Thanks for the report. If there is a spigot bug report, there will most likely be a fix soon. I have not updated to the latest spigot version for a while, will try to find some time this week to do that.