I'm having similar issues on my iPad 2 with iOS 9.2. If I have feature layers with more the a couple of hundred features, it crashes and reloads the page to the default extent.
I believe I have discovered the issue. It appears that using the halo in the label was causing the crashes for us. ESRI is in the process of validating that as a bug. When I turned off the halo in the label everything went back to normal.
We discovered this problem this morning and are able to reproduce it with only the ESRI satellite imagery base map turned on in the map. There is only one other layer in the map which is turned off and which does not have halos in the labels. When we zoom into about 2m/inch, the map crashes and the page reloads.
I am also experiencing this issue and have isolated the issue to the label halos on my address point feature class. I'm not sure if 1 or 500 halos are causing the crash, but when I turn them off everything works fine. Funny thing is, everything was fine until it wasn't. I think an update of either iOS or Safari caused the halos to crash the browser. I also tried it in Chrome on an Ipad so that leads me to believe it is an iOS update issue.