I'm having the same problem. I have an iPad Pro 10.5" running iOS 11. I can't say if this happened after the upgrade from iOS 10 to 11, but it sure seemed to happen around that time. I had TNFs created for band edges on each Amateur band, and now they're all gone, and I can't recreate any of them. The TNFs appear just fine on SmartSDR for Windows. Marcus, can you shed any light on this behavior?