Try
When a text or iMessage containing the text string is received and presented in the lock screen or as a drop-down notification, iOS gobbles up resources trying to render the message, ultimately causing Springboard to crash. The same line of code doesn't cause problems when received as part of a normal Messages conversation, suggesting the issue lies in part with iOS Notifications.
Some suggest turning off Messages previews for Notifications, though our tests have not shown this process to be effective. If Messages has already crashed, however, AppleInsider has confirmed that receiving a new message, sending out a picture from Photos or sending yourself a message through Share Sheets will stop the process.
From AppleInsider.