If the user edits a message, and the edited message is long, the receiver sees a truncated version of the message without the “Show more” option which is normally displayed for long messages, but the sender sees the full message displayed correctly in the chat and therefore thinks it was sent correctly.
This is an edge case so I maybe it is not worth fixing properly if it needs much effort, but there is a message integrity issue here because the sender and receiver see two different versions of the same message and the sender does not realize that the receiver sees something different.
Expected behavior
Either the receiver sees the full edited message, the receiver sees the “Show more” option for the long message, or the sender is warned that the edited message is too long to send correctly.
Actual behavior
The sender does not know that the receiver sees a truncated version of the edited message.