Angular8 Test different results for each run

I've joined a project based in Angular8.

Every time I run the tests I get a different results in my local machine. When I push my branch, in the Gitlab runner, I also have different results.

This is the way that we run the tests:

ng test --no-watch --no-progress --browsers=ChromeHeadlessCI

Those are the versions that we use:

"devDependencies": {
    "@angular-builders/custom-webpack": "^8.2.0",
    "@angular-devkit/build-angular": "^0.803.20",
    "@angular/cli": "^8.3.4",
    "@angular/compiler-cli": "^8.2.14",
    "@angular/language-service": "^8.2.6",
    "@types/jasmine": "^2.8.16",
    "@types/node": "^10.14.18",
    "@typescript-eslint/eslint-plugin": "^2.10.0",
    "@typescript-eslint/parser": "^2.10.0",
    "codelyzer": "^5.0.1",
    "eslint": "^6.7.2",
    "eslint-config-google": "^0.14.0",
    "jasmine-core": "^3.4.0",
    "jasmine-spec-reporter": "^4.2.1",
    "karma": "^3.1.4",
    "karma-chrome-launcher": "^2.2.0",
    "karma-cli": "^1.0.1",
    "karma-coverage-istanbul-reporter": "^2.1.0",
    "karma-htmlfile-reporter": "~0.3",
    "karma-jasmine": "^2.0.1",
    "karma-jasmine-html-reporter": "^1.4.2",
    "karma-junit-reporter": "^1.2.0",
    "protractor": "^5.4.2",
    "rxjs-tslint": "^0.1.7",
    "ts-node": "~7.0.1",
    "tslint": "^5.20.0",
    "typescript": "3.5.3",
    "webpack": "^4.41.2"
  } 

Sometimes I understand the test errors, like :

PatientClinicTrialsComponent should create FAILED
    Uncaught [object Object] thrown

I fixed that way:

if (examOrdersForPatient && examOrdersForPatient.length > 0) {

I added the if (examOrdersForPatient to the condition, so the Test is fixed.

But then, I have some errors in other components that have already passed the tests for my colleagues, like :

MessageComponent should create FAILED
    Uncaught [object Object] thrown

import { Component, OnInit, Inject, ViewEncapsulation } from '@angular/core';
import { DomSanitizer } from '@angular/platform-browser';
import { MatDialogRef, MAT_DIALOG_DATA } from '@angular/material/dialog';
import { DialogData } from '../shared/DialogData';

@Component({
  selector: 'envi-message',
  templateUrl: './message.component.html',
  styleUrls: ['./message.component.css'],
  host: { '(window:resize)': 'onResize($event)' }
})
export class MessageComponent implements OnInit {

  constructor(public dialogRef: MatDialogRef<MessageComponent>,
    public sanitizer: DomSanitizer,
    @Inject(MAT_DIALOG_DATA) public data: DialogData) { }

  ngOnInit() {
  }
}

This MessageComponent has "nothing" in the code. And it passed the tests for my colleagues.

I can't understand:

• Why I get different results in local tests and Gitlab runner (when the versions are equal)
• Why my branch (on Gitlab runner) is throwing error in tests components that are ok in my colleagues tests
• Is ng test randomly checking the components? I mean. Is it not testing everything in each run?

I'm sorry but I could'nt find a answer for all this problems. Thanks in advance.