This test failed once with:
[js_test:basicPlus] 2020-07-28T10:38:14.376+0000 Warning: localTimeSkew 506 > 50ms. [js_test:basicPlus] 2020-07-28T10:38:14.376+0000 assert: 506 is not less than 500 : isMaster.localTime
The test requires the shell to complete an isMaster in under half a second, but it took longer.