Minecraft: 1.10..2
Agricraft: 2.0.0.0.7.0-a12
When placing cropsticks on cropsticks you make a double cropstick.

Bug: You can keep applying these cropsticks onto those double cropsticks ad infinitum.
Breaking them only yields 2 cropsticks back.

Mods:
agricraft-2.0.0-0.7.0-a12
animania-1.10-1.0.2
AppleCore-mc1.10.2-2.1.2
AppleSkin-mc1.10.2-1.0.5
BlockDrops-1.10.2-1.1.1
CodeChickenCore-1.10.2-2.4.0.101-universal
CodeChickenLib-1.10.2-2.5.6.233-universal
compatlayer-1.10-0.2.2
Controlling-1.0.4
CookingForBlockheads_1.10.2-4.2.39
craftingharmonics-1.9.4_1.10_1.10.2-1.5.7.42
CraftingTweaks_1.10.2-6.1.16
CraftTweaker-1.10.2-3.0.24
extraalchemy-0.3.0.4-hotfix-release
HelpFixer-1.10.2-1.4.15
HungerOverhaul-1.10.2-1.1.0.jenkins111
Hwyla-1.8.11-B25_1.10.2
hydrogel-0.9
infinitylib-0.7.0
InitialInventory-1.0.1
intwheel-1.1x-1.2.4
InventoryTweaks-1.62-dev-66
itemscroller-1.10.2-0.10.3
jei_1.10.2-3.14.7.416
JustEnoughResources-1.10.2-0.5.9.3
JustEnoughTooltips-1.10.2-2.1.39
Lots of Food-1.12.0
Mantle-1.10.2-1.1.5
MineMenu-1.10.2-1.4.5-universal
ModTweaker2-2.0.10
MouseTweaks-2.8-mc1.10.2
MTLib-1.0.1
NashornLib-1.9.4-1.8.77-1.3.1.8
NotEnoughItems-1.10.2-2.1.3.201-universal
Pam's HarvestCraft 1.9.4-1.10.2h
PotionCore-1.4_for_1.10.2
SpiceOfLife-mc1.9.4-1.3.8
TConstruct-1.10.2-2.6.3
WailaHarvestability-mc1.10.2-1.1.9
Wawla-1.10.2-2.3.1.214

Can confirm this bug as well.

Fixed.