Receiving ERROR in Cannot read property 'fileName' of null during update from Angular 8 to Angular 9

Question

Unfortunately this error message gives absolutely zero context to what is going on and I have spent hours researching this. I have seen similar issues on stack but 0 solutions thus far. I would really appreciate any help anyone can offer as this is critical for my project.

Error

Image of the error above. I have been slowly but surely updating my Angular app from V6 to V9 today and I had no issues following the steps found here: https://update.angular.io/?v=6.0-9.0

I have been trimming down my package.json further and further trying to get to the bottom of this but nothing is helping.

package.json

{
  "name": "hertz-angular",
  "version": "0.0.0",
  "license": "MIT",
  "scripts": {
    "ng": "ng",
    "start": "ng serve --host 0.0.0.0",
    "build": "ng build --prod",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "^9.1.13",
    "@angular/cdk": "^9.1.0",
    "@angular/common": "^9.1.13",
    "@angular/compiler": "^9.1.13",
    "@angular/core": "^9.1.13",
    "@angular/forms": "^9.1.13",
    "@angular/material": "^9.1.0",
    "@angular/platform-browser": "^9.1.13",
    "@angular/platform-browser-dynamic": "^9.1.13",
    "@angular/router": "^9.1.13",
    "@ng-bootstrap/ng-bootstrap": "^6.2.0",
    "cors": "^2.8.5",
    "errorhandler": "^1.5.0",
    "express": "^4.16.4",
    "express-session": "^1.15.6",
    "morgan": "^1.9.1",
    "rxjs": "^6.6.7",
    "tslib": "^1.13.0",
    "zone.js": "~0.10.2"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "~0.901.15",
    "@angular/cli": "~9.1.15",
    "@angular/compiler-cli": "^9.1.13",
    "jasmine-core": "~2.8.0",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "^2.0.4",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "^1.2.1",
    "karma-jasmine": "~1.1.0",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "^5.3.2",
    "ts-node": "~4.1.0",
    "tslint": "~5.9.1",
    "typescript": "3.8.3"
  }
}