After every execution, regardless of said execution - when using Chrome web browser the PHP local server throws this error:
Invalid request (Unexpecte
This could be related to Chrome specifically and its network prediction feature. So try to disable that feature first. That's why it works for you in Incognito mode, because probably it's disabled in that mode.
You can find this option in Chrome Settings and click on 'Show advanced settings'. Should be there in Privacy section.