I found this issue when exploring world using both RTG generator and default. Here is log https://paste.ee/p/JSFhf
I also posted this issue to Fauna and Ecology dev.

Thanks.

• Modlist:
• [📁] 1.12 (folder)
• [❌] animania-1.12.2-1.7.3.jar (disabled)
• [✔️] AppleCore-mc1.12.2-3.4.0
• [✔️] AppleSkin-mc1.12-1.0.14
• [✔️] appliedenergistics2-rv6-stable-7
• [❌] armorunder-mc1.12.2-1.0.0.jar (disabled)
• [✔️] ASMC-1.12.2-1.0.2
• [✔️] AutoRegLib-1.3-32
• [✔️] BadMobs-1.12.2-1.1.40
• [✔️] BetterAdvancements-1.12.2-0.1.0.77
• [✔️] BetterDiving-1.12.2-1.5.7
• [❌] BetterFoliage-MC1.12-2.3.1.jar (disabled)
• [✔️] BetterFps-1.4.8
• [✔️] BetterQuesting-3.5.329
• [❌] BiblioCraft[v2.4.5][MC1.12.2].jar (disabled)
• [✔️] BiomesOPlenty-1.12.2-7.0.1.2444-universal
• [✔️] BiomeTweaker-1.12.2-3.2.368
• [✔️] BiomeTweakerCore-1.12.2-1.0.39
• [✔️] BNBGamingCore-1.12.2-0.12.0
• [✔️] BNBGamingLib-1.12.2-2.17.6
• [✔️] Bookshelf-1.12.2-2.3.590
• [✔️] Born+In+A+Barn+V1.8-1.12-1.1
• [❌] carrotslib-mc1.12.2-1.0.0b1.jar (disabled)
• [✔️] Ceramics-1.12-1.3.7
• [✔️] ClientTweaks_1.12.2-3.1.11
• [✔️] clothesline-1.12.2-0.0.3.0-bundle
• [✔️] CodeChickenLib-1.12.2-3.2.3.358-universal
• [✔️] comforts-1.12.2-1.4.1.3
• [❌] conarm-1.12.2-1.2.5.9.jar (disabled)
• [✔️] CookingForBlockheads_1.12.2-6.5.0
• [✔️] coroutil-1.12.1-1.2.37
• [✔️] corpse-1.12.2-1.0.8
• [❌] CraftStudioAPI-universal-1.0.1.95-mc1.12-alpha.jar (disabled)
• [✔️] CraftTweaker2-1.12-4.1.20.582
• [✔️] CreativeCore_v1.10.20_mc1.12.2
• [✔️] Cuisine-0.5.22-build929
• [✔️] dawnoftime_builder_edition-1.0.7
• [✔️] Divergent-Underground-1.12-0.64.0
• [❌] DrZharks MoCreatures Mod-12.0.5.zip (disabled)
• [✔️] DynamicSurroundings-1.12.2-3.6.1.0
• [✔️] DynamicTrees-1.12.2-0.9.8
• [✔️] DynamicTreesBOP-1.12.2-1.4.1e
• [❌] dynamictreesForestry-1.12.2-1.0.4.jar (disabled)
• [❌] dynamictreesNatura-1.12.2-1.1.0.jar (disabled)
• [❌] DynamicTreesPHC-1.12.2-1.4.2.jar (disabled)
• [✔️] Exotic+Birds+1.12.2-3.2.0
• [❌] fairylights-2.1.11-1.12.2.jar (disabled)
• [✔️] FE-1.12.2-0.1.3.1
• [❌] firstaid-1.6.14.jar (disabled)
• [✔️] foamfix-0.10.10-1.12.2
• [❌] forestry_1.12.2-5.8.2.387.jar (disabled)
• [✔️] Forgelin-1.8.4
• [✔️] ForgeMultipart-1.12.2-2.6.2.83-universal
• [✔️] gamestagebooks-1.12.2-1.0.2-universal
• [✔️] GameStages-1.12.2-2.0.123
• [✔️] Geolosys-1.12.2-3.0.10
• [✔️] HardcoreDarkness-MC1.12.2-2.0
• [✔️] ido-1.12.2-1.1.0
• [✔️] ImmersiveEngineering-0.12-98
• [✔️] ItemPhysic_Full_1.4.34_mc1.12.2
• [✔️] ItemStages-1.12.2-2.0.49
• [✔️] IvToolkit-1.3.3-1.12
• [✔️] jei_1.12.2-4.15.0.297
• [✔️] Kiwi-1.12.2-0.5.3.32
• [✔️] LittleTiles_v1.5.0-pre199_44_mc1.12.2
• [✔️] Mantle-1.12-1.3.3.55
• [✔️] matmos-1.12.2-35.1
• [📁] memory_repo (folder)
• [✔️] MrTJPCore-1.12.2-2.1.4.43-universal
• [❌] natura-1.12.2-4.3.2.69.jar (disabled)
• [✔️] nature-overhaul-1.3.1
• [✔️] NaturesCompass-1.12.2-1.8.5
• [✔️] NotEnoughPets-1.12.2-v2.2.0
• [✔️] Nutrition-1.12.2-4.6.1
• [❌] OptiFine_1.12.2_HD_U_E3.jar (disabled)
• [✔️] OreLib-1.12.2-3.6.0.1
• [✔️] outfox-0.1.5-mc1.12.2
• [❌] Pam's HarvestCraft 1.12.2zg.jar (disabled)
• [✔️] phosphor-1.12.2-0.2.6+build50-universal
• [❌] Photoptics-1.12.2-0.1.1.1.jar (disabled)
• [❌] PlayersChoice+1.2-5.jar (disabled)
• [✔️] PrettyBeaches_1.12.2-1.0.4
• [❌] primitivecrafting-1.12.2-1.4.4.7.jar (disabled)
• [✔️] ProjectRed-1.12.2-4.9.4.120-Base
• [✔️] ProjectRed-1.12.2-4.9.4.120-fabrication
• [✔️] ProjectRed-1.12.2-4.9.4.120-integration
• [✔️] ProjectRed-1.12.2-4.9.4.120-lighting
• [✔️] ProjectRed-1.12.2-4.9.4.120-mechanical
• [✔️] ProjectRed-1.12.2-4.9.4.120-world
• [✔️] Quark-r1.6-179
• [✔️] questbook-3.1.1-1.12
• [✔️] randompatches-1.12.2-1.22.1.1
• [✔️] RealFirstPerson2-1.12.2-1.3.2
• [✔️] RealisticBlockPhysics-1.12.2-1.2.2
• [✔️] RecipeStages-1.1.3
• [✔️] RecurrentComplex-1.4.8.2
• [✔️] ResourceLoader-MC1.12.1-1.5.3
• [✔️] RTG-1.12.2-6.1.0.0-snapshot.1
• [✔️] rustic-1.1.5
• [✔️] SereneSeasons-1.12.2-1.2.18-universal
• [✔️] SimpleDifficulty-1.12.2-0.3.0
• [✔️] SnowRealMagic-0.3.3
• [✔️] Sound-Physics-1.12.2-1.0.9
• [✔️] StandardExpansion-3.4.173
• [❌] Stellar+API-1.12.2-0.4.2.9.jar (disabled)
• [❌] Stellar+Sky-1.12.2-0.5.2.8.jar (disabled)
• [❌] Surge-1.12.2-2.0.77.jar (disabled)
• [❌] SurvivalInc-v1.1.5.jar (disabled)
• [✔️] survivalistlighting-1.12.2-6
• [✔️] TConstruct-1.12.2-2.13.0.183
• [✔️] theoneprobe-1.12-1.4.28
• [✔️] TidyChunk-1.12.2-1.0.0.0
• [✔️] TinkersComplement-1.12.2-0.4.3
• [❌] TravelersBackpack-1.12.2-1.0.33.jar (disabled)
• [✔️] Triumph-1.12.2-3.19.2
• [✔️] tropicraft-MC1.12.2-7.1.9.115
• [✔️] VanillaFix-1.0.10-150
• [✔️] Waddles-1.12.2-0.6.0
• [❌] weather2-1.12.1-2.6.12.jar (disabled)
• [✔️] World-Stripper-1.6.0-1.12.2
• [✔️] worleycaves-1.5.

Version 1.1.6
Fixed! Thanks for your very quick response!

I got to mention! Rustic is probably my favorite mod now. Reminds me of the old days when RedPower 2 was a thing. The amount of atmosphere and quality this mod has is that big that it might be in every modpack ever made!
Thanks for doing that! :D