1.12.2

v.3.6.1 (betweenlands)
14.23.5.2847 (forge version)
Singleplayer

Installed mods:

micdoodlecore
xaerominimap_core1.12.2-1.0
| [1.12.2]+SecurityCraft+v1.8.17.jar
| [1.12.2]DamageIndicatorsMod-
jei_1.12.2-4.15.0.291.jar
athenaeum-1.12.2-1.18.1.jar
CodeChickenLib-1.12.2-3.2.3.358-universal.jar
| RedstoneFlux-1.12-2.1.1.1-universal.jar
BrandonsCore-1.12.2-2.4.18.210-universal.jar
car-1.12.2-2.0.1.jar
| cdm-0.4.1-mc1.12.2.jar
| cfm-6.3.0-mc1.12.2.jar
| CTM-MC1.12.2-1.0.2.31.jar
| Chisel-MC1.12.2-1.0.2.45.jar
| CoFHCore-1.12.2-4.6.6.1-universal.jar
| CoFHWorld-1.12.2-1.4.0.1-universal.jar
CustomMobSpawner-3.11.4.jar
| ThermalFoundation-1.12.2-2.6.3.27-universal.jar
| Draconic-Evolution-1.12.2-2.3.25.351-universal.jar
| dropt-1.12.2-1.18.0.jar
| | DrZharks-Mocreatures-Mod-12.0.4.jar
| DynamicTrees-1.12.2-0.9.8.jar
| Flan's Mod-1.12.2-5.5.2.jar
| wumpleutil-1.12.2-2.12.9.jar
| foodfunk-1.12.2-4.9.6.jar
| industrialcraft-2-2.8.197-ex112.jar
GalacticraftCore-1.12.2-4.0.2.244.jar
Galacticraft-Planets-1.12.2-4.0.2.244.jar
ICBM-classic-1.12.2-3.3.0b63.jar
InfernalMobs-1.12.1.jar
| ironchest-1.12.2-7.0.72.847.jar
|MCA-1.12.2-6.1.0-universal.jar
Mekanism-1.12.2-9.7.1.372.jar
| MineMenu-1.12.2-1.6.10-universal.jar
| | llibrary-1.7.19-1.12.2.jar
| mowziesmobs-1.5.4.jar
| | Pam's+BrewCraft+1.12.2-1.0.1.jar
| Pam's+HarvestCraft+1.12.2zg.jar
| pyrotech-1.12.2-1.4.23.jar
| L | SchopCraft-0.3.1-for-MC-1.12.2.jar
| ThermalInnovation-1.12.2-0.3.6.1-universal.jar
| TravellersBackpack-1.12.2-1.0.23.23.jar
| update+4.jar
| VariedCommodities_1.12.2(21nov19).jar
| | Xaeros_Minimap_20.5.0_Forge_1.12.jar
| TheBetweenlands-3.6.1-universal.jar

to full crash log
https://pastebin.com/FMZiF05f

ok so I'm playing with around 50 mods and i try to place a flans mod plane my screen freezes and my game crashes

This seems to be unrelated to Betweenlands, and the same crash seemed to happen without Betweenlands installed: FlansMods/FlansMod#1125. Try updating Flan's mods.