DataAPI writing error, Sponge v4.1.0-SNAPSHOT (currently 4.0.3)

nbt_error.log

/*
This happens after writing to the sign, though the DataTransactionResult says it succeeds, I don't think it does (have to double-check).
The first one happens when secondary(right)-clicking the sign.
The second one then happens every so often afterwards.
After restarting the server, there is no sign-text anymore.

This is my plugin, Fedora's Market, built off of Sponge 4.1.0-SNAPSHOT, JDK 1.8.0_77.
The server is running on Forge 1764, Sponge 4.0.3.
*/
[17:27:03] [Server thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.IllegalArgumentException: Unable to translate object to NBTBase!
        at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.8.0_71]
        at java.util.concurrent.FutureTask.get(Unknown Source) ~[?:1.8.0_71]
        at net.minecraft.util.Util.func_181617_a(SourceFile:45) [g.class:?]
        at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:660) [MinecraftServer.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:344) [ko.class:?]
        at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:605) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:481) [MinecraftServer.class:?]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_71]
Caused by: java.lang.IllegalArgumentException: Unable to translate object to NBTBase!
        at org.spongepowered.common.data.persistence.NbtTranslator.getBaseFromObject(NbtTranslator.java:166) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.getBaseFromObject(NbtTranslator.java:152) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.getBaseFromObject(NbtTranslator.java:152) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.containerToCompound(NbtTranslator.java:91) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.containerToCompound(NbtTranslator.java:72) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.translateData(NbtTranslator.java:287) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at net.minecraft.tileentity.TileEntity.writeToNbt(TileEntity.java:239) ~[akw.class:?]
        at net.minecraft.tileentity.TileEntity.handler$onWriteToNBT$0(TileEntity.java:183) ~[akw.class:?]
        at net.minecraft.tileentity.TileEntity.func_145841_b(TileEntity.java) ~[akw.class:?]
        at net.minecraft.tileentity.TileEntitySign.func_145841_b(TileEntitySign.java:34) ~[aln.class:?]
        at net.minecraft.world.World.createSnapshot(World.java:787) ~[adm.class:?]
        at net.minecraftforge.event.entity.player.PlayerInteractEvent.handler$onConstructed$0(PlayerInteractEvent.java:75) ~[PlayerInteractEvent.class:?]
        at net.minecraftforge.event.entity.player.PlayerInteractEvent.<init>(PlayerInteractEvent.java:69) ~[PlayerInteractEvent.class:?]
        at net.minecraftforge.event.ForgeEventFactory.onPlayerInteract(ForgeEventFactory.java:56) ~[ForgeEventFactory.class:?]
        at net.minecraft.server.management.ItemInWorldManager.func_180236_a(ItemInWorldManager.java:403) ~[lg.class:?]
        at net.minecraft.network.NetHandlerPlayServer.redirect$onActivateBlockOrUseItem$0(NetHandlerPlayServer.java:110) ~[lm.class:?]
        at net.minecraft.network.NetHandlerPlayServer.func_147346_a(NetHandlerPlayServer.java:588) ~[lm.class:?]
        at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:59) ~[ja.class:?]
        at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:10) ~[ja.class:?]
        at org.spongepowered.common.network.PacketUtil.onProcessPacket(PacketUtil.java:106) ~[PacketUtil.class:1.8.9-1763-4.1.0-BETA-1201]
        at net.minecraft.network.PacketThreadUtil$1.redirect$onProcessPacket$0(SourceFile:51) ~[fh$1.class:?]
        at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[fh$1.class:?]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_71]
        at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_71]
        at net.minecraft.util.Util.func_181617_a(SourceFile:44) ~[g.class:?]
        ... 5 more
[17:27:21] [Server thread/ERROR] [FML]: A TileEntity type net.minecraft.tileentity.TileEntitySign has throw an exception trying to write state. It will not persist. Report this to the mod author
java.lang.IllegalArgumentException: Unable to translate object to NBTBase!
        at org.spongepowered.common.data.persistence.NbtTranslator.getBaseFromObject(NbtTranslator.java:166) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.getBaseFromObject(NbtTranslator.java:152) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.getBaseFromObject(NbtTranslator.java:152) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.containerToCompound(NbtTranslator.java:91) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.containerToCompound(NbtTranslator.java:72) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at org.spongepowered.common.data.persistence.NbtTranslator.translateData(NbtTranslator.java:287) ~[NbtTranslator.class:1.8.9-1763-4.1.0-BETA-1201]
        at net.minecraft.tileentity.TileEntity.writeToNbt(TileEntity.java:239) ~[akw.class:?]
        at net.minecraft.tileentity.TileEntity.handler$onWriteToNBT$0(TileEntity.java:183) ~[akw.class:?]
        at net.minecraft.tileentity.TileEntity.func_145841_b(TileEntity.java) ~[akw.class:?]
        at net.minecraft.tileentity.TileEntitySign.func_145841_b(TileEntitySign.java:34) ~[aln.class:?]
        at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75820_a(AnvilChunkLoader.java:368) [anj.class:?]
        at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75816_a(AnvilChunkLoader.java:165) [anj.class:?]
        at net.minecraft.world.gen.ChunkProviderServer.func_73242_b(ChunkProviderServer.java:238) [ld.class:?]
        at net.minecraft.world.gen.ChunkProviderServer.func_73151_a(ChunkProviderServer.java:298) [ld.class:?]
        at net.minecraft.world.WorldServer.func_73044_a(WorldServer.java:905) [le.class:?]
        at net.minecraft.server.MinecraftServer.func_71267_a(MinecraftServer.java:366) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:628) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:481) [MinecraftServer.class:?]

Solved, can only have primitives stored in DataView.