A friend of mine noticed that on our server the Summon Skeleton Horse spell crashed his game when he used it. I then started a single player world to test out if any of the other mods I was using where causing the issue. When I started the game with only Electroblobs Wizardry and Ancient Spellcraft I still had the issue.
If I use a scroll it does not crash and nothing happens, but if I use a wand it crashes.
crash-2021-04-29_18.04.51-server.txt

fixed in 32b638e