Toggling a redstone comparator in a specific contraption throws an exception

[youFailerEXE]

Expected behavior

Toggling a redstone comparator in any contraption on and then off should not throw an exception.

Observed/Actual behavior

Upon turning the comparator on then off in the contraption, this exception is thrown:

[19:10:13 WARN]: com.destroystokyo.paper.exception.ServerInternalException: Trying to set block entity net.minecraft.world.level.block.entity.ComparatorBlockEntity@2f9016a8 at position BlockPos{x=91, y=70, z=94}, but state Block{minecraft:air} does not allow it [19:10:13 WARN]: at net.minecraft.world.level.chunk.LevelChunk.setBlockEntity(LevelChunk.java:533) [19:10:13 WARN]: at net.minecraft.world.level.chunk.LevelChunk.addAndRegisterBlockEntity(LevelChunk.java:503) [19:10:13 WARN]: at net.minecraft.world.level.chunk.LevelChunk.setBlockState(LevelChunk.java:440) [19:10:13 WARN]: at net.minecraft.world.level.Level.setBlock(Level.java:1089) [19:10:13 WARN]: at net.minecraft.world.level.Level.setBlock(Level.java:1047) [19:10:13 WARN]: at net.minecraft.world.level.block.ComparatorBlock.useWithoutItem(ComparatorBlock.java:139) [19:10:13 WARN]: at net.minecraft.world.level.block.state.BlockBehaviour$BlockStateBase.useWithoutItem(BlockBehaviour.java:929) [19:10:13 WARN]: at net.minecraft.server.level.ServerPlayerGameMode.useItemOn(ServerPlayerGameMode.java:560) [19:10:13 WARN]: at net.minecraft.server.network.ServerGamePacketListenerImpl.handleUseItemOn(ServerGamePacketListenerImpl.java:2155) [19:10:13 WARN]: at net.minecraft.network.protocol.game.ServerboundUseItemOnPacket.handle(ServerboundUseItemOnPacket.java:45) [19:10:13 WARN]: at net.minecraft.network.protocol.game.ServerboundUseItemOnPacket.handle(ServerboundUseItemOnPacket.java:10) [19:10:13 WARN]: at net.minecraft.network.PacketProcessor$ListenerAndPacket.handle(PacketProcessor.java:99) [19:10:13 WARN]: at net.minecraft.network.PacketProcessor.executeSinglePacket(PacketProcessor.java:33) [19:10:13 WARN]: at net.minecraft.server.MinecraftServer.pollTask(MinecraftServer.java:1533) [19:10:13 WARN]: at net.minecraft.server.MinecraftServer.recordTaskExecutionTimeWhileWaiting(MinecraftServer.java:1263) [19:10:13 WARN]: at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1379) [19:10:13 WARN]: at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:304) [19:10:13 WARN]: at java.base/java.lang.Thread.run(Thread.java:1474)

Steps/models to reproduce

1. Go to 91, 73, 93 in the world or paste the schematic.
2. Find the redstone comparator that has its single torch adjacent to a wool block and its double torch adjacent to the composter, as shown in the screenshot.
3. Right click the comparator twice. It should break, and the exception should show up in the logs

contraption schematic.zip

world.zip

Plugin and Datapack List

plugins
[19:51:36 INFO]: ℹ Server Plugins (0):

datapack list
[19:51:49 INFO]: There are 3 data pack(s) enabled: [vanilla (built-in)], [file/bukkit (world)], [paper (built-in)]
[19:51:49 INFO]: There are no more data packs available

Paper version

ver
[19:51:13 INFO]: Checking version, please wait...
[19:51:13 INFO]: This server is running Paper version 26.1.2-18-main@6bac3c9 (2026-04-20T10:18:10Z) (Implementing API version 26.1.2.build.18-alpha)
You are running the latest version
Previous version: 26.1.2-15-66d3bbe (MC: 26.1.2)

Other

No response

[xt449]

Seems to be an upstream vanilla bug.
Paper just logs the stack trace.
There is a slight inconsistency between the block popping off or not, but I suspect that it just the Paper anti-dupe working.