We are sorry about this inconvenience. We believe this is about grouping. To ungroup notes, please go to our help page, https://help.zoho.com/portal/kb/articles/how-to-ungroup-notecards. Please try this and get back to us.
We are sorry that you have to face such issues with the app. We request you to kindly open the note, tap on 'More'(3 vertical dots placed at the top right), select versions and check if you could see the actual content. If this doesn't help you, please send us a feedback from the which will help us in analyzing this issue further.