Fabric 0.11.6
Fabric API 0.37.0
Mod version 2.3.1

When I place minecart hoppers in a chunk, I am then unable to save the world and log is spammed with this message

[22:05:13] [Server thread/ERROR]: Failed to save chunk 121,-72
net.minecraft.class_148: Saving entity NBT
at net.minecraft.class_1297.method_5647(class_1297.java:1577) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_1297.method_5786(class_1297.java:1502) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_1297.method_5662(class_1297.java:1510) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_2852.method_12410(class_2852.java:301) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_3898.method_17228(class_3898.java:716) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_3898.method_20583(class_3898.java:388) ~[intermediary-1.16.5.jar:?]
at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183) ~[?:?]
at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:179) ~[?:?]
at java.util.Iterator.forEachRemaining(Iterator.java:133) ~[?:?]
at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801) ~[?:?]
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484) ~[?:?]
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474) ~[?:?]
at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) ~[?:?]
at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) ~[?:?]
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[?:?]
at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596) ~[?:?]
at net.minecraft.class_3898.method_17242(class_3898.java:385) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_3215.method_17298(class_3215.java:321) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_3218.method_14176(class_3218.java:710) ~[intermediary-1.16.5.jar:?]
at net.minecraft.server.MinecraftServer.method_3723(MinecraftServer.java:567) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_1132.method_3748(class_1132.java:83) ~[intermediary-1.16.5.jar:?]
at net.minecraft.server.MinecraftServer.handler$cai000$modifiedRunLoop(MinecraftServer.java:8310) ~[intermediary-1.16.5.jar:?]
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:651) ~[intermediary-1.16.5.jar:?]
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:257) ~[intermediary-1.16.5.jar:?]
at java.lang.Thread.run(Thread.java:831) [?:?]
Caused by: java.lang.NullPointerException: Cannot invoke "net.minecraft.class_2371.size()" because "?" is null
at net.minecraft.class_1262.method_5427(class_1262.java:35) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_1262.method_5426(class_1262.java:30) ~[intermediary-1.16.5.jar:?]
at net.flytre.hplus2.hopper.HopperPlus.hplusToTag(HopperPlus.java:30) ~[better-hoppers-2.3.1.jar:?]
at net.minecraft.class_1700.handler$beo000$hplus$toTag(class_1700.java:581) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_1700.method_5652(class_1700.java) ~[intermediary-1.16.5.jar:?]
at net.minecraft.class_1297.method_5647(class_1297.java:1559) ~[intermediary-1.16.5.jar:?]
... 24 more

latest.log