What may be the reason of this:
It waits for more than 30 minutes there and then moves on. Why it takes so much time after Finished requesting crash reports. Continuing with testing.?
Here is how my lane for testing is defined:
lane :test do
    scan(scheme: SCHEME_NAME, code_coverage: true, clean: true, output_directory: OUTPUT_PATH + 'tests', devices: ["iPhone 8 Plus"], reset_simulator: true, disable_concurrent_testing: true)
end

