I'm having the same issue, and I discovered what the problem is but not how to fix it. The problem: Whenever I attach an image to my text message, the program is selecting that application (from where I grabbed the attachment) as the default app. So if I attach a photo from Gallery, then the next time I try to attach something it will only offer my images from my Gallery. If I clear the SMS defaults so I can attach a Bitmoji, then that becomes the default and the only image I can attach next time is from the Bitmoji application. Would love to clear all defaults and have them stay that way...