What is "failed to scene-update in time" crash

Question

[ Wow. No "community" for mail app (or other built-in apps), crashes, iOS 8 (or just iOS). ]
iPad 2 running IOS 8 for a week or so. Sluggish and battery draining faster than before, but all apps were working ok. Then during an attempt to delete an e-mail the mail app crashed. Now it crashes every time I try to start or access it. Crash log (moved in iOS 8 to be under Privacy instead of General > About) says the error is "failed to scene-update in time". I've done an Internet search and found little info about this error and it's all questions with no solutions.
I have closed the app and tried to re-open it. I have shutdown the device and restarted. I have disabled my ISP mail (pop, not IMAP) and iCloud mail expecting the app to then prompt me to setup mail. Always this error. I would prefer not to delete the data unless or until there's good reason to try that.
My iPhone 5 is still on IOS 7 and mail is working fine there.

Answer 1

Well, here's a hint. Apparently the notification message has changed from iOS 7.1 to iOS8.1
I got the same behavior/crash on my app as well and captured crash logs for each OS:
7.1 says:
Incident Identifier: 1AFAD8D6-50B3-4B5A-8EBE-2A76E4400BDA
CrashReporter Key:   8e228dccf0b7ae7d1127923c96eec86495483eae
Hardware Model:      iPhone5,3
Process:             ProcessName [2967]
Path:                /var/mobile/Applications/key/myApp.app
Identifier:          com.company.app
Version:             5.6.0042 (5.6)
Code Type:           ARM (Native)
Parent Process:      launchd [1]
Date/Time:           2014-11-04 17:32:57.089 -0800
OS Version:          iOS 7.1.1 (11D201)
Report Version:      104
Exception Type:  00000020
Exception Codes: 0x000000008badf00d
Highlighted Thread:  0
Application Specific Information:
com.company.app failed to resume in time
While iOS 8.1 says:
Incident Identifier: 960DB688-F165-4DCD-98A1-3F4AEFFB5442
CrashReporter Key:   2022d4aa4b6f69db15c58ae02734fb8172a77bba
Hardware Model:      iPhone7,2
Process:             ProcessName [175]
Path:                /private/var/mobile/Containers/Bundle/Application/key/myApp.app
Identifier:          com.company.app
Version:             5.6.0042 (5.6)
Code Type:           ARM-64 (Native)
Parent Process:      launchd [1]
Date/Time:           2014-11-04 18:05:31.933 -0800
Launch Time:         2014-11-04 17:30:28.408 -0800
OS Version:          iOS 8.1 (12B411)
Report Version:      105
Exception Type:  00000020
Exception Codes: 0x000000008badf00d
Highlighted Thread:  0
Application Specific Information:
com.company.app failed to scene-update in time
So, pretty much everything is the same except for the Application Specific Information section.
In our case there was a method running on the Main thread that wasn't completing therefore it was getting the rest of the UI stuck and the system was killing it.
In your case though the APP runs fine on iOS 7 so it might be a different root cause.