i can't seem to be able to put milk into the skeleton builders, i'm not exactly sure of it, but i'm almost certain some other mod changed either the milk itself or the handling of liquids and buckets in general and Overlord isn't recognizing the milk as it's fluid "fuel" anymore.

right, forgot about that:
AdvancedRocketry
agricraft
AkashicTome
architecturecraft
astikoor
AutoRegLib
Baubles
BetterFps
BiblioCraft
Chameleon
CodeChickenLib
colytra
CombinedPotions
culinaryconstruct
cyberware
Earthworks
EnderStorage
Erebus
extraalchemy
ExtraRails
FenceOverhaul
FluidGenerators
foamfix
GardenStuff
Grim+Pack
Guide-API
Hwyla
iceandfire
ImmersiveEngineering

that's... not all... damn, gonna have to see them all manually, not all's in the log...

in any case, JEI says the milk bucket has been added by tinkers, so i heavily suspect it is the main cause here, perhaps with some help from unidict...

07/29/2018 17:51 11,582,504 AdvancedRocketry-1.12.2-1.4.0-93-universal.jar
07/29/2018 18:38 1,342,279 agricraft-2.12.0-1.12.0-a5.jar
07/29/2018 19:21 43,608 AkashicTome-1.2-10.jar
07/29/2018 18:37 897,626 architecturecraft-1.12-2.68.jar
07/30/2018 00:06 59,693 astikoor-1.0.0.jar
07/29/2018 19:21 84,923 AutoRegLib-1.3-18.jar
08/01/2018 22:17 108,450 Baubles-1.12-1.5.2.jar
07/29/2018 19:23 155,196 BetterFps-1.4.8.jar
07/29/2018 18:32 5,122,856 BiblioCraft[v2.4.5][MC1.12.2].jar
07/29/2018 18:27 96,859 Chameleon-1.12-4.1.3.jar
07/29/2018 17:54 700,157 CodeChickenLib-1.12.2-3.2.1.349-universal.jar
08/01/2018 22:17 82,913 colytra-1.12.2-1.1.0.jar
08/06/2018 00:36 12,972 CombinedPotions-1.12-1.1.jar
07/30/2018 00:19 81,690 culinaryconstruct-1.1.1.jar
08/06/2018 00:39 913,778 cyberware-1.12.2-0.2.10.13.jar
07/30/2018 00:27 705,301 Earthworks-1.12-1.3.6.jar
07/29/2018 18:32 223,227 EnderStorage-1.12.2-2.4.5.135-universal.jar
07/29/2018 19:15 12,597,272 Erebus-1.0.22.jar
07/30/2018 00:30 216,180 extraalchemy-0.3.8.5-release.jar
07/30/2018 00:12 53,565 ExtraRails-1.12-1.3.0.jar
07/29/2018 19:06 40,845 FenceOverhaul-1.3.4.jar
08/06/2018 06:58 196,745 FluidGenerators1-0-3.jar
07/29/2018 19:24 206,359 foamfix-0.9.9.1-1.12.2-anarchy.jar
07/30/2018 00:26 158,782 GardenStuff-1.12-2.1.1.jar
08/06/2018 01:27 6,525,580 Grim+Pack-1.12.2-5.2.12.78.jar
08/06/2018 01:54 168,974 Guide-API-1.12-2.1.6-61.jar
08/04/2018 00:24 453,778 Hwyla-1.8.26-B41_1.12.2.jar
07/29/2018 17:35 12,711,831 iceandfire-1.5.2.jar
07/29/2018 19:23 6,097,870 ImmersiveEngineering-0.12-84.jar
07/29/2018 19:23 906,018 immersivepetroleum-1.12.2-1.1.9.jar
08/01/2018 22:12 858,298 infinitylib-1.12.0.jar
07/30/2018 00:10 467,773 JAOPCA-1.12.2-2.2.8.91.jar
07/30/2018 00:20 43,001 JAOPCAAdditions-1.12.2-2.2.1.9.jar
07/29/2018 18:28 575,409 jei_1.12.2-4.11.0.202.jar
07/30/2018 00:20 18,945 JustEnoughPetroleum-0.1.jar
08/01/2018 22:13 496,220 LibVulpes-1.12.2-0.2.8-36-universal.jar
07/29/2018 19:20 867,352 llibrary-1.7.14-1.12.2.jar
07/29/2018 18:01 860,884 Mantle-1.12-1.3.2.24.jar
08/06/2018 01:53 295,872 MechSoldiers-1.12.2-1.1.6.jar
08/04/2018 02:06 33,622 MmmMmmMmmMmm-1.12-1.14.jar
07/30/2018 00:25 70,754 moartinkers-0.6.0.jar
07/29/2018 16:42 82,455 moon-core+7.0+(1.12).jar
07/29/2018 16:53 8,867,761 NaturalFauna+Mod-1.0.0.jar
07/30/2018 00:31 8,640 nomoreglowingpots-1.0.jar
08/05/2018 23:15 33,549 NoMoreRecipeConflict-0.11(1.12.2).jar
08/06/2018 07:05 5,729 noslimes-1.12.2-1.0.jar
07/29/2018 18:27 470,129 NotEnoughItems-1.12.2-2.4.1.238-universal.jar
08/06/2018 01:39 534,256 Overlord-1.12.2-2.4.10.jar
07/29/2018 18:54 610,245 placeableitems-3.3.jar
08/05/2018 23:27 359,796 plustic-6.5.2.0.jar
07/30/2018 00:07 64,037 RealisticItemDrops-1.2.12.jar
08/06/2018 01:35 306,405 ReWIRED-1.0.3.jar
07/30/2018 00:50 1,308,330 rustic-1.0.6.jar
07/29/2018 18:39 464,802 ShadowMC-1.12-3.8.0.jar
07/30/2018 00:48 24,024 stg-1.12.2-1.2.3.jar
07/29/2018 18:27 596,191 StorageDrawers-1.12.2-5.3.7.jar
08/11/2018 12:36 3,810,539 TConstruct-1.12.2-2.10.1.87.jar
08/06/2018 01:16 44,044 Tinkers'+Addons-1.12.1-1.0.7.jar
07/30/2018 00:55 167,871 TinkersComplement-1.12.2-0.2.3b.jar
08/15/2018 22:33 2,203,794 tinkersdefense-1.4.2.18a.jar
07/29/2018 18:23 178,275 UniDict-1.12.2-2.5f.jar
07/29/2018 19:22 5,401,579 Valkyrien+Warfare+0.9_prerelease_5+[Optimization+Update].jar
07/30/2018 00:44 31,462 WailaHarvestability-mc1.12-1.1.12.jar
07/29/2018 19:20 63,189 WanionLib-1.12.2-1.5.jar
07/30/2018 00:44 83,630 Wawla-1.12.2-2.5.257.jar
07/30/2018 00:10 25,417 WrapUp-1.12-1.1.3.jar
08/12/2018 02:45 79,185 XpHolder-1.0.1-mc1.12.x.jar
07/29/2018 16:43 11,434,158 zawa+-+1.3.2+(1.12.2).jar
07/29/2018 18:31 35,549 [1.12]MoVillages-1.5.4.jar

sorry for the extra junk, copied using command prompt coz it was easier and wasn't at all that patient to delet everything unneeded(very sorry)

Forge is no longer being supported, and the mod is getting a total rewrite for Fabric. Here's why.