This was a bug in a previous version of the app; I have not heard it occurring since. Are you using the most recent version (4.0.2) of Sketch? If not, can you update?
Please let me know if that resolves the issue.
Thank you so much for answering. Could you please tell me how to update? I am using version 3.4.1 I have looked and can’t figure out how to update it. I’m nervous about losing the pictures. Thank you so much for your help!
Yes. This is the version of the app that had the bug. You should see the update (for v 4.0.2) in the App Store app on your device (tap the Updates icon).
If you want to make sure, before you update, that your work is synced/saved to the cloud, log in with your Adobe ID to Adobe Creative Cloud and make sure that you see all the work there that you see on your device. Then install the update.
Let me know if you have trouble.