EntityBat has two fields:
private static final DataParameter<Byte> HANGING
private BlockPos spawnPosition

In your preInit(), you're calling EntityBat.class.getDeclaredFields()[0], presumably to get the spawnPosition field. However, according to the documentation for Class.getDeclaredFields():

The elements in the returned array are not sorted and are not in any particular order.

So under some circumstances, you'll get the spawnPosition field as desired, while under others, you'll get the HANGING field, wild bats will ignore pie, and the log will spit out this error:

[04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: java.lang.IllegalAccessException: Can not set static final net.minecraft.network.datasync.DataParameter field net.minecraft.entity.passive.EntityBat.field_184660_a to net.minecraft.util.math.BlockPos [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at sun.reflect.UnsafeFieldAccessorImpl.throwFinalFieldIllegalAccessException(UnsafeFieldAccessorImpl.java:76) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at sun.reflect.UnsafeFieldAccessorImpl.throwFinalFieldIllegalAccessException(UnsafeFieldAccessorImpl.java:80) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at sun.reflect.UnsafeQualifiedStaticObjectFieldAccessorImpl.set(UnsafeQualifiedStaticObjectFieldAccessorImpl.java:77) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.lang.reflect.Field.set(Field.java:764) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at atomicstryker.petbat.common.PetBatMod.lambda$onPlayerLeftClick$1(PetBatMod.java:232) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at atomicstryker.petbat.common.PetBatMod$$Lambda$525/171636232.accept(Unknown Source) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at atomicstryker.petbat.common.PetBatMod.onPlayerLeftClick(PetBatMod.java:229) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_188_PetBatMod_onPlayerLeftClick_BreakSpeed.invoke(.dynamic) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:179) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraftforge.event.ForgeEventFactory.getBreakSpeed(ForgeEventFactory.java:170) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.entity.player.EntityPlayer.getDigSpeed(EntityPlayer.java:836) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraftforge.common.ForgeHooks.blockStrength(ForgeHooks.java:232) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.block.Block.func_180647_a(Block.java:559) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.block.state.BlockStateContainer$StateImplementation.func_185903_a(BlockStateContainer.java:408) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.client.multiplayer.PlayerControllerMP.func_180511_b(PlayerControllerMP.java:246) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.client.Minecraft.func_147116_af(Minecraft.java:1516) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.client.Minecraft.redirect$onClickMouse$zzj000(Minecraft.java:3480) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.client.Minecraft.func_184117_aA(Minecraft.java:2247) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.client.Minecraft.func_184118_az(Minecraft.java:2018) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1806) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1096) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:397) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.client.main.Main.main(SourceFile:123) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at java.lang.reflect.Method.invoke(Method.java:497) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [04:55:51] [main/INFO]: [atomicstryker.petbat.common.PetBatMod:lambda$onPlayerLeftClick$1:236]: at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

c47f14b
Thank you for reporting this, you are correct