Why do physical devices crash accidentally change the XCTest UI tests?

Question

Why do physical devices crash accidentally change the XCTest UI tests?

Recently, when writing new tests and testing on physical devices (in some cases, sometimes several times during tests or sometimes after several hours of testing), each device starts to fail. The only solution I found was to restart the device and then the tests would start working fine again.

Here is the console output from Xcode 7.3.1:

2016-07-22 09:17:27.277 XCTRunner[470:164209] Running tests...
2016-07-22 09:17:27.280 XCTRunner[470:164209] Unable to load configuration data from specified path /var/folders/83/tbqj_hp908ddc7bn45hcrh_c0000gn/T/com.apple.dt.XCTest/B389F86E-56B0-4131-B52B-8E9A41E2A789/remote-container/tmp/CollaborateUITests-B389F86E-56B0-4131-B52B-8E9A41E2A789.xctestconfiguration; error: The file doesn’t exist.
2016-07-22 09:17:27.281 XCTRunner[470:164209] Looking for test bundles in /var/containers/Bundle/Application/15D4EDF6-C56A-4735-9DEF-57869AE677AC/CollaborateUITests-Runner.app/PlugIns
2016-07-22 09:17:27.281 XCTRunner[470:164209] Found test bundle at /var/containers/Bundle/Application/15D4EDF6-C56A-4735-9DEF-57869AE677AC/CollaborateUITests-Runner.app/PlugIns/CollaborateUITests.xctest
2016-07-22 09:17:27.282 XCTRunner[470:164209] Looking for configurations in /var/containers/Bundle/Application/15D4EDF6-C56A-4735-9DEF-57869AE677AC/CollaborateUITests-Runner.app/PlugIns/CollaborateUITests.xctest
2016-07-22 09:17:27.282 XCTRunner[470:164209] No configurations found, creating a default configuration that will run all tests.
2016-07-22 09:17:27.480 XCTRunner[470:164209] *** Assertion failure in -[XCUIApplication init], /Library/Caches/com.apple.xbs/Sources/XCTest_iOS/XCTest-10112/XCTestFramework/UI Testing/XCUIApplication.m:72

And pthread_kill:

libsystem_kernel.dylib`__pthread_kill:
    0x180620114 <+0>:  movz   x16, #0x148
    0x180620118 <+4>:  svc    #0x80
->  0x18062011c <+8>:  b.lo   0x180620134               ; <+32>
    0x180620120 <+12>: stp    x29, x30, [sp, #-16]!
    0x180620124 <+16>: mov    x29, sp
    0x180620128 <+20>: bl     0x1806066d8               ; cerror_nocancel
    0x18062012c <+24>: mov    sp, x29
    0x180620130 <+28>: ldp    x29, x30, [sp], #16
    0x180620134 <+32>: ret