How to replicate:
create a function file with one of these two commands:
give @s stone{display:{Name:"§ctest"}}

results in either an instant game crash, or a game crash when you look at the item/mob.
Most likely due to the new name formatting differences.

This is especially problematic for worlds that have pre-existing data packs, functions, custom items, mobs, commands, etc.

Extra note: this appears to work fine with "Lore"

Crash report:
Unreported exception thrown!
com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1 path $
at com.google.gson.internal.Streams.parse(Streams.java:60)
at com.google.gson.internal.bind.TreeTypeAdapter.read(TreeTypeAdapter.java:65)
at vf.a(SourceFile:493)
at vf.a(SourceFile:518)
at hn$a.a(SourceFile:241)
at anp.q(SourceFile:508)
at bon.c(SourceFile:584)
at bon.a(SourceFile:231)
at cao.a(SourceFile:979)
at bnv.b(SourceFile:822)
at bnv.a(SourceFile:382)
at net.minecraft.client.main.Main.main(SourceFile:140)
Caused by: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1 path $
at com.google.gson.stream.JsonReader.syntaxError(JsonReader.java:1559)
at com.google.gson.stream.JsonReader.checkLenient(JsonReader.java:1401)
at com.google.gson.stream.JsonReader.doPeek(JsonReader.java:593)
at com.google.gson.stream.JsonReader.peek(JsonReader.java:425)
at com.google.gson.internal.Streams.parse(Streams.java:46)
... 11 more