Minecraft version: 1.12.2
Wizardry version: 4.3.4
Environment: Singleplayer

Issue details: Friendly wizards usually despawn. To reproduce- 1) Find a wizard in his tower. 2) Leave the area for a while. 3) Return to where you found him. 4) Be sad because dad went to get magic crystals and never came back.

Other mods involved: It's a very small pack, so I've listed them all in case there's a known conflict between Wizardry and one of the others.

afarmk-0.3.jar
AncientSpellcraft-1.12.2-1.2.0.jar
anvilpatch-1.1.0.jar
Baubles-1.12-1.5.2.jar
BetterCombat-1.12.2-1.5.6.jar
BetterFps-1.4.8.jar
collective-1.12.2-2.26.jar
copypaste-1.1.jar
craftdumper-1.12.2-1.3.0.jar
defaultenchantments-1.12.2-1.3.0.jar
ElectroblobsWizardry-4.3.4-MC1.12.2.jar
endportalrecipe_1.12.2-2.3.jar
ExtraGolems-1.12-7.1.9.jar
FantasticLib-1.12.2.047.jar
firespreadtweaks_1.12.2-1.1.jar
foamfix-0.10.14-1.12.2.jar
Forgelin-1.8.4.jar
GottschCore-mc1.12.2-f14.23.5.2854-v1.14.0.jar
gravestone-1.10.3.jar
Hwyla-1.8.26-B41_1.12.2.jar
InventoryTweaks-1.63.jar
jei_1.12.2-4.16.1.302.jar
journeymap-1.12.2-5.7.0.jar
mcjtylib-1.12-3.5.4.jar
MouseTweaks-2.10.1-mc1.12.2.jar
nonetherPortals_v1.0.0formc1.12.2.jar
notenoughwands-1.12-1.8.1.jar
OptiFine_1.12.2_HD_U_G5.jar
phosphor-1.12.2-0.2.6+build50-universal.jar
rad-1.12-1.1.0.jar
SetBonus-1.12.2.020.jar
Surge-1.12.2-2.0.77.jar
TFSpellPack-1.1.0-MC1.12.2.jar
Treasure2-mc1.12.2-f14.23.5.2854-v1.16.1 (1).jar
Treasure2TwilightForestLP-mc1.12.2-f14.23.5.2854-v1.0.0.jar
Treasure2WizardryLP-mc1.12.2-f14.23.5.2854-v1.0.0.jar
twilightforest-1.12.2-3.11.1021-universal.jar
VanillaFix-1.0.10-99.jar
Wawla-1.12.2-2.6.274.jar
WizardryGolems-1.0.1.jar
WizardryTales-1.0.0.jar

Link to crash report (if applicable): N/A

Edit: After experimenting a bit, I have determined that this is a bug with the Ancient Spellcraft addon. Now reported on that mod's github.