EarlGrey:Failed to execute block because idling resources below are busy

Question

I ran the following commands and it says failed to execute block because idling resources below are busy.

EarlGrey.select(elementWithMatcher: grey_accessibilityLabel("First Label")).atIndex(0).perform(grey_tap())

EarlGrey.select(elementWithMatcher: grey_accessibilityLabel("Second Label")).perform(grey_tap())

The second label is on navigation bar at the top. On click of that button screen slides.

Error trace:

Exception Details: Error Trace: [
  {
    "Description" : "Failed to execute block because idling resources below are busy.",
    "Description Glossary" :     {
      "UIWebView Pre-Load Tracker" : "UIWebView Pre-Load Tracker"
    },
    "Domain" : "com.google.earlgrey.GREYUIThreadExecutorErrorDomain",
    "Code" : "0",
    "File Name" : "GREYUIThreadExecutor.m",
    "Function Name" : "-[GREYUIThreadExecutor executeSyncWithTimeout:block:error:]",
    "Line" : "235",
    "TestCase Class" : "EarlgreyAutomation.FeedAutomation",
    "TestCase Method" : "testUserShouldWatchFlightAndSeeItsList"
  },
  {
    "Description" : "Failed to execute assertion within 30 seconds.",
    "Domain" : "com.google.earlgrey.ElementInteractionErrorDomain",
    "Code" : "4",
    "File Name" : "GREYElementInteraction.m",
    "Function Name" : "-[GREYElementInteraction assert:error:]",
    "Line" : "418",
    "TestCase Class" : "EarlgreyAutomation.FeedAutomation",
    "TestCase Method" : "testUserShouldWatchFlightAndSeeItsList"
  }
]

I tried to resolve this by changing value of kGREYConfigKeyDelayedPerformMaxTrackableDuration to threshold - 1 but no progress.