TypeError: Cannot read property 'buildError' of undefined. What can it be?

Tried to "ember server" an application, but have got following error:

The Broccoli Plugin: [broccoli-persistent-filter:Babel > [Babel: inboxfront]: Babel: inboxfront] failed with:
TypeError: Cannot read property 'buildError' of undefined

Here are the details:

    at Scope.checkBlockScopedCollisions (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/scope/index.js:344:22)
    at Scope.registerBinding (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/scope/index.js:501:16)
    at Scope.registerDeclaration (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/scope/index.js:441:14)
    at Object.BlockScoped (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/scope/index.js:187:28)
    at Object.newFn (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/visitors.js:230:17)
    at NodePath._call (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/path/context.js:53:20)
    at NodePath.call (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/path/context.js:36:14)
    at NodePath.visit (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/path/context.js:88:12)
    at TraversalContext.visitQueue (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/context.js:118:16)
    at TraversalContext.visitMultiple (/home/username/inboxfrontend/node_modules/@babel/traverse/lib/context.js:85:17)

The broccoli plugin was instantiated at: 
    at Babel.Plugin (/home/username/inboxfrontend/node_modules/broccoli-plugin/index.js:7:31)
    at Babel.Filter [as constructor] (/home/username/inboxfrontend/node_modules/broccoli-persistent-filter/index.js:64:10)
    at new Babel (/home/username/inboxfrontend/node_modules/ember-cli-babel/node_modules/broccoli-babel-transpiler/index.js:37:10)
    at Class.transpileTree (/home/username/inboxfrontend/node_modules/ember-cli-babel/index.js:48:16)
    at Object.toTree (/home/username/inboxfrontend/node_modules/ember-cli-babel/index.js:58:30)
    at /home/username/inboxfrontend/node_modules/ember-cli-preprocess-registry/preprocessors.js:180:26
    at Array.forEach (<anonymous>)
    at processPlugins (/home/username/inboxfrontend/node_modules/ember-cli-preprocess-registry/preprocessors.js:178:11)
    at module.exports.preprocessJs (/home/username/inboxfrontend/node_modules/ember-cli-preprocess-registry/preprocessors.js:171:10)
    at EmberApp.appAndDependencies (/home/username/inboxfrontend/node_modules/ember-cli/lib/broccoli/ember-app.js:1254:27)

Also

DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: inboxfront -> ember-highcharts -> ember-getowner-polyfill -> ember-cli-babel
DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: inboxfront -> ember-paper-stepper -> ember-cli-babel
Could not start watchman
Visit https://ember-cli.com/user-guide/#watchman for more info.
was unable to use: "events", fell back to: "polling"
Livereload server on http://localhost:7020

Don't you know what can it be?