If the app crashes after receiving a message
- Place your phone in Airplane mode.
- Open Signal.
- Long-press to highlight the MMS/offending message.
- Tap the trash can to delete the message and confirm yes.
- Take your phone out of airplane mode.
If the app continues crashing
- Use another app to request a contact send you a message.
- Receive a new message.
- Use the notification or quick reply feature of the new received message to mark all messages as read.