In case anyone sees this thread...I found the app and device that was leading to surpassing the 1024 character limit. It's this app, and due to a huge calendar invite description in my Google calendar:
What I didn't figure out was why the mobile app was identifying it when none of my dashboards were setup to use that app's device (not just not used in a tile, but not reserved for use by any of the dashboards). If anyone has any thoughts on that part, please let me know?