Application modifying the autolayout engine from a background thread causes crash on keyboard focus

Hi there,

We're getting issues when keyboard focus is given to a textbox within a form. Upon clicking the form field, the entire app immediately crashes and the following information is displayed in Xcode:

2015-10-08 18:47:49.092 BudiPay[527:113011] This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes. This will cause an exception in a future release.
Stack
0 CoreFoundation 0x0000000184608f74 <redacted> + 148
1 libobjc.A.dylib 0x0000000199af7f80 objc_exception_throw + 56
2 CoreFoundation 0x0000000184608ea4 <redacted> + 0
3 Foundation 0x00000001856225d8 <redacted> + 88
4 Foundation 0x00000001854a4a1c <redacted> + 36
5 UIKit 0x0000000189c6393c <redacted> + 64
6 UIKit 0x0000000189c64454 <redacted> + 244
7 UIKit 0x0000000189c80f28 <redacted> + 108
8 UIKit 0x000000018a38a77c <redacted> + 268
9 UIKit 0x0000000189e61fb0 <redacted> + 176
10 UIKit 0x0000000189e51098 <redacted> + 52
11 UIKit 0x0000000189b5aff0 <redacted> + 644
12 QuartzCore 0x0000000189361f14 <redacted> + 148
13 QuartzCore 0x000000018935cb20 <redacted> + 292
14 QuartzCore 0x000000018935c9e0 <redacted> + 32
15 QuartzCore 0x000000018935c07c <redacted> + 252
16 QuartzCore 0x000000018935bdd0 <redacted> + 516
17 QuartzCore 0x00000001893aeb00 <redacted> + 592
18 IOKit 0x0000000185896018 IODispatchCalloutFromCFMessage + 372
19 CoreFoundation 0x00000001845aa8e0 <redacted> + 180
20 CoreFoundation 0x00000001845c0cdc <redacted> + 56
21 CoreFoundation 0x00000001845c0414 <redacted> + 436
22 CoreFoundation 0x00000001845be16c <redacted> + 1800
23 CoreFoundation 0x00000001844ecdc0 CFRunLoopRunSpecific + 384
24 WebCore 0x0000000196a25aa0 <redacted> + 456
25 libsystem_pthread.dylib 0x000000019a4fbb3c <redacted> + 156
26 libsystem_pthread.dylib 0x000000019a4fbaa0 <redacted> + 0
27 libsystem_pthread.dylib 0x000000019a4f9030 thread_start + 4
)
2015-10-08 18:47:49.096 BudiPay[527:113011] This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes. This will cause an exception in a future release.
Stack
0 CoreFoundation 0x0000000184608f74 <redacted> + 148
1 libobjc.A.dylib 0x0000000199af7f80 objc_exception_throw + 56
2 CoreFoundation 0x0000000184608ea4 <redacted> + 0
3 Foundation 0x00000001856225d8 <redacted> + 88
4 Foundation 0x00000001854a8f3c <redacted> + 56
5 Foundation 0x00000001854a4afc <redacted> + 260
6 UIKit 0x0000000189c6393c <redacted> + 64
7 UIKit 0x0000000189c64454 <redacted> + 244
8 UIKit 0x0000000189c80f28 <redacted> + 108
9 UIKit 0x000000018a38a77c <redacted> + 268
10 UIKit 0x0000000189e61fb0 <redacted> + 176
11 UIKit 0x0000000189e51098 <redacted> + 52
12 UIKit 0x0000000189b5aff0 <redacted> + 644
13 QuartzCore 0x0000000189361f14 <redacted> + 148
14 QuartzCore 0x000000018935cb20 <redacted> + 292
15 QuartzCore 0x000000018935c9e0 <redacted> + 32
16 QuartzCore 0x000000018935c07c <redacted> + 252
17 QuartzCore 0x000000018935bdd0 <redacted> + 516
18 QuartzCore 0x00000001893aeb00 <redacted> + 592
19 IOKit 0x0000000185896018 IODispatchCalloutFromCFMessage + 372
20 CoreFoundation 0x00000001845aa8e0 <redacted> + 180
21 CoreFoundation 0x00000001845c0cdc <redacted> + 56
22 CoreFoundation 0x00000001845c0414 <redacted> + 436
23 CoreFoundation 0x00000001845be16c <redacted> + 1800
24 CoreFoundation 0x00000001844ecdc0 CFRunLoopRunSpecific + 384
25 WebCore 0x0000000196a25aa0 <redacted> + 456
26 libsystem_pthread.dylib 0x000000019a4fbb3c <redacted> + 156
27 libsystem_pthread.dylib 0x000000019a4fbaa0 <redacted> + 0
28 libsystem_pthread.dylib 0x000000019a4f9030 thread_start + 4
)
2015-10-08 18:47:49.097 BudiPay[527:113011] *** Assertion failure in -[UIApplication _cachedSystemAnimationFenceCreatingIfNecessary:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit/UIKit-3505.17/UIApplication.m:1697
2015-10-08 18:47:49.098 BudiPay[527:113011] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'accessing _cachedSystemAnimationFence requires the main thread'

• • • First throw call stack:
      (0x184608f5c 0x199af7f80 0x184608e2c 0x1854f7f3c 0x189dfb0cc 0x189dfb190 0x189e4d3b0 0x18a2fb788 0x18a2f613c 0x189e5dfac 0x189bbb698 0x189c66a24 0x189b7669c 0x1844ffab0 0x1844ff9a8 0x189b653cc 0x189c66b6c 0x189e621f4 0x189b5aff0 0x189361f14 0x18935cb20 0x18935c9e0 0x18935c07c 0x18935bdd0 0x1893aeb00 0x185896018 0x1845aa8e0 0x1845c0cdc 0x1845c0414 0x1845be16c 0x1844ecdc0 0x196a25aa0 0x19a4fbb3c 0x19a4fbaa0 0x19a4f9030)
      libc++abi.dylib: terminating with uncaught exception of type NSException
      (lldb)

In the xcode window when connected to the process:

libsystem_kernel.dylib`__pthread_kill:
0x19a4331d8 <+0>: movz x16, #0x148
0x19a4331dc <+4>: svc #0x80
-> 0x19a4331e0 <+8>: b.lo 0x19a4331f8 ; <+32>
0x19a4331e4 <+12>: stp x29, x30, sp, #-16!
0x19a4331e8 <+16>: mov x29, sp
0x19a4331ec <+20>: bl 0x19a41a330 ; cerror_nocancel
0x19a4331f0 <+24>: mov sp, x29
0x19a4331f4 <+28>: ldp x29, x30, [sp], #16
0x19a4331f8 <+32>: ret

We're using the Ionic framework, but they have referred us here from there: https://github.com/driftyco/ionic/issues/4402

Seems like a number of people receiving the same issue. Apologies if I haven't provided enough information - happy to field questions or help to debug further. (Have tried to format the above as code, but Jira won't let me)