The bug

When you give yourself an item with the display tag with custom name, such as
/give @s minecraft:pumpkin{display:{Name:"ItemName"}}
the game crashes instantly and on the crash report the following error appears:

Description: Unexpected error

com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1 path

Also, the world gets corrupted and it crashes when you try to play it.