When clicking on a text component that has a run_command click event, the value is treated as a command instead of a message. For text in books and in chat specifically, this means that the preceding slash must now not be included for the command to run. Commands on signs still work with the preceding slash.

Steps to reproduce:

Run the command /tellraw @s {"text":"click me","clickEvent":

Click the message

What I expected to happen:

The /say hi command would run

What actually happened:

I received an error:
Unknown or incomplete command, see below for error
/say hi<--[HERE]