What are you trying to achieve?

Very similar to #6519:
When I do
codecept run
everything is green, but when I do
codecept run --coverage
I get an error. The exakt output is below.
There is also a file _output\App.Tests.Acceptance.HomepageCest.testIndexPage.fail.html, that only consists of on error message:

<html><head></head><body><br>
<b>Fatal error</b>:  Uncaught ErrorException: Warning: Cannot modify header information - headers already sent in D:\Apps\Apache\DSCA\c3.php:52
Stack trace:
#0 D:\Apps\Apache\DSCA\c3.php(264): __c3_error()
#1 D:\Apps\Apache\DSCA\c3.php(390): __c3_factory()
#2 [internal function]: {closure}()
#3 {main}
  thrown in <b>D:\Apps\Apache\DSCA\c3.php</b> on line <b>52</b><br>
</body></html>

What do you get instead?

Provide console output if related. Use -vvv mode for more details.

D:\Apps\Apache\DSCA>codecept run tests\acceptance\HomepageCest.php --coverage -vvv
==== Redirecting to Composer-installed version in vendor/codeception. You can skip this using --no-redirect ====
Codeception PHP Testing Framework v5.0.0 https://helpukrainewin.org
App\Tests.acceptance Tests (1) ----------------------------------------------------------------------------------------------------------------------------------------------------------------------Modules: WebDriver, \App\Tests\Helper\Acceptance, Asserts, \Sanitas\TestHelper\Module\ConfigHelper
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------⏺ Recording ⏺ step-by-step screenshots will be saved to D:\Apps\Apache\DSCA\tests/_output</info>
Directory Format: record_62e930a5cdfb5_{filename}_{testname} ----
HomepageCest: Test index page
Signature: App\Tests\Acceptance\HomepageCest:testIndexPage
Test: tests\acceptance\HomepageCest.php:testIndexPage
Scenario --
  [GET] http://127.0.0.1:2777/
  [Cookies] [{"name":"CODECEPTION_CODECOVERAGE","value":"{\"CodeCoverage\":\"testIndexPage\",\"CodeCoverage_Suite\":\"App\\\\Tests.acceptance\",\"CodeCoverage_Config\":null}","path":"/","domain":"127.0.0.1","expiry":1659535913,"secure":false,"httpOnly":false}]
 I am on page "/"
  [GET] http://127.0.0.1:2777/
  [Cookies] [{"name":"CODECEPTION_CODECOVERAGE","value":"{\"CodeCoverage\":\"testIndexPage\",\"CodeCoverage_Suite\":\"App\\\\Tests.acceptance\",\"CodeCoverage_Config\":null}","path":"/","domain":"127.0.0.1","expiry":1659535913,"secure":false,"httpOnly":false}]
  Screenshot and page source were saved into 'D:\Apps\Apache\DSCA\tests/_output\' dir
 ERROR
In LocalServer.php line 163:
  [RuntimeException]
  Code coverage file D:\Apps\Apache\DSCA\tests/_output\c3tmp/codecoverage.serialized does not exist
Exception trace:
  at D:\Apps\Apache\DSCA\vendor\codeception\codeception\src\Codeception\Coverage\Subscriber\LocalServer.php:163
 Codeception\Coverage\Subscriber\LocalServer->afterSuite() at D:\Apps\Apache\DSCA\vendor\symfony\event-dispatcher\EventDispatcher.php:230
 Symfony\Component\EventDispatcher\EventDispatcher->callListeners() at D:\Apps\Apache\DSCA\vendor\symfony\event-dispatcher\EventDispatcher.php:59
 Symfony\Component\EventDispatcher\EventDispatcher->dispatch() at D:\Apps\Apache\DSCA\vendor\codeception\codeception\src\Codeception\SuiteManager.php:150
 Codeception\SuiteManager->run() at D:\Apps\Apache\DSCA\vendor\codeception\codeception\src\Codeception\Codecept.php:260
 Codeception\Codecept->runSuite() at D:\Apps\Apache\DSCA\vendor\codeception\codeception\src\Codeception\Codecept.php:216
 Codeception\Codecept->run() at D:\Apps\Apache\DSCA\vendor\codeception\codeception\src\Codeception\Command\Run.php:442
 Codeception\Command\Run->execute() at D:\Apps\Apache\DSCA\vendor\symfony\console\Command\Command.php:298
 Symfony\Component\Console\Command\Command->run() at D:\Apps\Apache\DSCA\vendor\symfony\console\Application.php:1024
 Symfony\Component\Console\Application->doRunCommand() at D:\Apps\Apache\DSCA\vendor\symfony\console\Application.php:299
 Symfony\Component\Console\Application->doRun() at D:\Apps\Apache\DSCA\vendor\symfony\console\Application.php:171
 Symfony\Component\Console\Application->run() at D:\Apps\Apache\DSCA\vendor\codeception\codeception\src\Codeception\Application.php:112
 Codeception\Application->run() at D:\Apps\Apache\DSCA\vendor\codeception\codeception\app.php:45
 {closure}() at D:\Apps\Apache\DSCA\vendor\codeception\codeception\app.php:46
 require() at C:\Users\p.garstenauer\AppData\Roaming\Composer\vendor\codeception\codeception\autoload.php:13
 require_once() at C:\Users\p.garstenauer\AppData\Roaming\Composer\vendor\codeception\codeception\app.php:3
 require() at C:\Users\p.garstenauer\AppData\Roaming\Composer\vendor\codeception\codeception\codecept:7
run [-o|--override OVERRIDE] [-e|--ext EXT] [--report] [--html [HTML]] [--xml [XML]] [--phpunit-xml [PHPUNIT-XML]] [--colors] [--no-colors] [--silent] [--steps] [-d|--debug] [--shard SHARD] [--filter FILTER] [--grep GREP] [--bootstrap [BOOTSTRAP]] [--no-redirect] [--coverage [COVERAGE]] [--coverage-html [COVERAGE-HTML]] [--coverage-xml [COVERAGE-XML]] [--coverage-text [COVERAGE-TEXT]] [--coverage-crap4j [COVERAGE-CRAP4J]] [--coverage-cobertura [COVERAGE-COBERTURA]] [--coverage-phpunit [COVERAGE-PHPUNIT]] [--no-exit] [-g|--group GROUP] [-s|--skip SKIP] [-x|--skip-group SKIP-GROUP] [--env ENV] [-f|--fail-fast [FAIL-FAST]] [--no-rebuild] [--seed SEED] [--no-artifacts] [--] [<suite> [<test>]]

Details

Codeception version: 5.0.0
PHP Version: 8.0.10
Operating System: Windows
Installation type: Composer
List of installed packages (composer show)
Suite configuration:

actor: AcceptanceTester
modules:
    enabled:
        - WebDriver:
            url: 'http://127.0.0.1:2777/'
            browser: chrome
            window_size: 976x636
            capabilities:
                "acceptInsecureCerts": true
                "goog:chromeOptions":
                    args: ["--headless", "--disable-gpu", "--disable-extensions"]
        - \App\Tests\Helper\Acceptance
        - Asserts
        - \Sanitas\TestHelper\Module\ConfigHelper
extensions:
    enabled:
        - Codeception\Extension\Recorder:
            delete_successful: true