mathjs: ERROR TypeError: Cannot convert 2546 to type "undefined"; valid output types are number, BigNumber, Fraction

Hello, I’m trying to use the evaluate() method to do some math using a string in an Angular application. This is my method:

calculateMileageCharge() {
    let formula = this.worksheet.mileageChargeRef;

    formula = formula.replace('${firstMileage}', this.worksheet.firstMileage.toString();
    formula = formula.replace('${purPrice}', this.mainForm.get('purPrice').value);

    this.worksheet.mileageChargeRefCal = evaluate(formula);
  }

The formula var works out to be: “2546 * (9988 / 120000)” but any formula (i.e. 2*3) throws the same error with the first number in the formula.

This all works fine while developing, but as soon as I use ng build --prod i get the error in the title. Building without --prod works fine.

This is my package.json, in case it helps. The prod build uses the “build:prod” script:

{
  "name": "bbms",
  "version": "0.2.0",
  "scripts": {
    "ng": "ng",
    "postinstall": "node version.js",
    "start": "ng serve -c localapi",
    "start:devapi": "ng serve -c devapi",
    "start:localapi": "ng serve -c localapi",
    "build": "ng build",
    "build:prod": "npm version minor --no-git-tag-version && node version.js && ng build --prod  --baseHref=/bbms/ --deploy-url=/bbms/resources/bbms/",
    "build:prodMajor": "npm version major --no-git-tag-version && node version.js && ng build --prod  --baseHref=/bbms/ --deploy-url=/bbms/resources/bbms/",
    "build:prodPatch": "npm version patch --no-git-tag-version && node version.js && ng build --prod  --baseHref=/bbms/ --deploy-url=/bbms/resources/bbms/",
    "build:prodNoVer": "ng build --prod  --baseHref=/bbms/ --deploy-url=/bbms/resources/bbms/",
    "build:eclipse": "ng build --configuration=eclipse --output-path=../webapp/resources/bbms --baseHref=/bbms/ --deploy-url=/bbms/resources/bbms/",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "^7.2.2",
    "@angular/cdk": "^7.2.2",
    "@angular/common": "^7.2.10",
    "@angular/compiler": "^7.2.10",
    "@angular/core": "^7.2.10",
    "@angular/flex-layout": "^7.0.0-beta.24",
    "@angular/forms": "~7.2.2",
    "@angular/material": "^7.2.2",
    "@angular/platform-browser": "~7.2.2",
    "@angular/platform-browser-dynamic": "~7.2.2",
    "@angular/router": "~7.2.2",
    "@fortawesome/angular-fontawesome": "^0.3.0",
    "@fortawesome/fontawesome-svg-core": "^1.2.12",
    "@fortawesome/free-solid-svg-icons": "^5.6.3",
    "@types/mathjs": "^6.0.0",
    "angular-file": "^1.2.2",
    "angular-in-memory-web-api": "^0.8.0",
    "core-js": "^2.5.4",
    "fs-extra": "^8.1.0",
    "google-libphonenumber": "^3.2.2",
    "hammerjs": "^2.0.8",
    "jquery": "^3.4.1",
    "libphonenumber-js": "^1.7.15",
    "mathjs": "^6.0.3",
    "ng2-file-upload": "^1.3.0",
    "ngx-infinite-scroll": "^7.1.0",
    "ngx-spinner": "^7.1.4",
    "rxjs": "~6.3.3",
    "tslib": "^1.9.0",
    "zone.js": "~0.8.26"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "^0.12.4",
    "@angular/cli": "^7.3.6",
    "@angular/compiler-cli": "^7.2.10",
    "@angular/language-service": "~7.2.2",
    "@ryaneharris/bbms-schematics": "^0.1.1",
    "@types/google-libphonenumber": "^7.4.17",
    "@types/jasmine": "~3.3.8",
    "@types/jasminewd2": "~2.0.3",
    "@types/jquery": "^3.3.29",
    "@types/node": "~10.12.18",
    "codelyzer": "~4.5.0",
    "jasmine-core": "~3.3.0",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "~4.0.0",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "~2.0.1",
    "karma-jasmine": "~2.0.1",
    "karma-jasmine-html-reporter": "^1.4.0",
    "protractor": "~5.4.0",
    "ts-node": "~8.0.1",
    "tslint": "~5.12.1",
    "typescript": "~3.2.4"
  }
}

Let me know if you need more info.

Thanks!