Difficulty deleting messages

When I try to delete one or more messages by pressing and holding on a message, then selecting More... from the pop up, the trash can icon doesn't always appear as expected. (It only appears about 15% of the time.) I must then close out of the Messages app completely and restart Messages before the trash can icon replaces the camera icon. Sometimes after successfully deleting several messages, I try to select more messages for deletion from a different thread and again the trash can does not always replace the camera icon. Using an iPhone 6 with iOS 8.1.2