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`yarn start` is failing sometimes

See original GitHub issue

Here’s an error that @benknight got when trying to start the repo.

$ ../../scripts/should-build-package.js -- rollup -c=../../rollup.config.js
$ ../../scripts/should-build-package.js -- rollup -c=../../rollup.config.js
$ ../../scripts/should-build-package.js -- rollup -c=../../rollup.config.js
$ ../../scripts/should-build-package.js -- rollup -c=../../rollup.config.js
lerna success run Ran npm script 'prepublishOnly' in packages:
lerna success - @thumbtack/thumbprint-atomic
lerna success - @thumbtack/thumbprint-tokens
lerna success - @thumbtack/tp-ui-react-avatar
lerna success - @thumbtack/tp-ui-react-button-row
lerna success - @thumbtack/tp-ui-react-button
lerna success - @thumbtack/tp-ui-react-carousel
lerna success - @thumbtack/tp-ui-react-checkbox
lerna success - @thumbtack/tp-ui-react-date-picker
lerna success - @thumbtack/tp-ui-react-form-note
lerna success - @thumbtack/tp-ui-react-grid
lerna success - @thumbtack/tp-ui-react-input-row
lerna success - @thumbtack/tp-ui-react-input
lerna success - @thumbtack/tp-ui-react-label
lerna success - @thumbtack/tp-ui-react-link
lerna success - @thumbtack/tp-ui-react-list
lerna success - @thumbtack/tp-ui-react-loader-dots
lerna success - @thumbtack/tp-ui-react-modal-base
lerna success - @thumbtack/tp-ui-react-modal-curtain
lerna success - @thumbtack/tp-ui-react-modal-default
lerna success - @thumbtack/tp-ui-react-modal-standard
lerna success - @thumbtack/tp-ui-react-progress-bar-base
lerna success - @thumbtack/tp-ui-react-progress-bar
lerna success - @thumbtack/tp-ui-react-radio
lerna success - @thumbtack/tp-ui-react-select
lerna success - @thumbtack/tp-ui-react-service-card
lerna success - @thumbtack/tp-ui-react-star-rating
lerna success - @thumbtack/tp-ui-react-textarea
lerna success - @thumbtack/tp-ui-react-tooltip
lerna success - @thumbtack/tp-ui-react-type
lerna success - @thumbtack/tp-ui-react-ui-action
lerna success - @thumbtack/tp-ui-react-wrap

ℹ️  Need a hand? Reach out on #design-systems for help.

$ gatsby develop --port 8090
success open and validate gatsby-config — 0.121 s
success load plugins — 0.305 s
success onPreInit — 1.048 s
success delete html and css files from previous builds — 0.055 s
success initialize cache — 0.006 s
success copy gatsby files — 0.261 s
success onPreBootstrap — 0.021 s
error Cannot read property 'children' of undefined


  TypeError: Cannot read property 'children' of undefined

  - actions.js:50 children.concat.children.map.child
    [www]/[gatsby]/dist/redux/actions.js:50:39

  - Array.map

  - actions.js:49 findChildrenRecursively
    [www]/[gatsby]/dist/redux/actions.js:49:42

  - actions.js:300 actions.deleteNode.args
    [www]/[gatsby]/dist/redux/actions.js:300:29

  - bindActionCreators.js:7
    [thumbtack-thumbprint]/[redux]/lib/bindActionCreators.js:7:35

  - source-nodes.js:74 staleNodes.forEach.node
    [www]/[gatsby]/dist/utils/source-nodes.js:74:34

  - Array.forEach

  - source-nodes.js:74
    [www]/[gatsby]/dist/utils/source-nodes.js:74:18

  - Generator.next

  - util.js:16 tryCatcher
    [thumbtack-thumbprint]/[bluebird]/js/release/util.js:16:23

  - promise.js:512 Promise._settlePromiseFromHandler
    [thumbtack-thumbprint]/[bluebird]/js/release/promise.js:512:31

  - promise.js:569 Promise._settlePromise
    [thumbtack-thumbprint]/[bluebird]/js/release/promise.js:569:18

  - promise.js:614 Promise._settlePromise0
    [thumbtack-thumbprint]/[bluebird]/js/release/promise.js:614:10

  - promise.js:694 Promise._settlePromises
    [thumbtack-thumbprint]/[bluebird]/js/release/promise.js:694:18


error UNHANDLED REJECTION


  TypeError: Cannot read property 'children' of undefined

  - actions.js:50 children.concat.children.map.child
    [www]/[gatsby]/dist/redux/actions.js:50:39

  - Array.map

  - actions.js:49 findChildrenRecursively
    [www]/[gatsby]/dist/redux/actions.js:49:42

  - actions.js:300 actions.deleteNode.args
    [www]/[gatsby]/dist/redux/actions.js:300:29

  - bindActionCreators.js:7
    [thumbtack-thumbprint]/[redux]/lib/bindActionCreators.js:7:35

  - source-nodes.js:74 staleNodes.forEach.node
    [www]/[gatsby]/dist/utils/source-nodes.js:74:34

  - Array.forEach

  - source-nodes.js:74
    [www]/[gatsby]/dist/utils/source-nodes.js:74:18

  - Generator.next

  - util.js:16 tryCatcher
    [thumbtack-thumbprint]/[bluebird]/js/release/util.js:16:23

  - promise.js:512 Promise._settlePromiseFromHandler
    [thumbtack-thumbprint]/[bluebird]/js/release/promise.js:512:31

  - promise.js:569 Promise._settlePromise
    [thumbtack-thumbprint]/[bluebird]/js/release/promise.js:569:18

  - promise.js:614 Promise._settlePromise0
    [thumbtack-thumbprint]/[bluebird]/js/release/promise.js:614:10

  - promise.js:694 Promise._settlePromises
    [thumbtack-thumbprint]/[bluebird]/js/release/promise.js:694:18


error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.