I'm looking for suggestion on how to start troubleshooting this issue: We have simple PHP/MYSQL app that worked flawlessly until last week. All of a sudden after logging in we are redirected to root domain (inventory.domain.com -> www.domain.com).
We can see that login was successful - main menu appears for a millisecond, before it's redirected.
I tried with different browsers and different machines.
It's on premise server without access from internet.
Is there way to track when and by what part of code is redirect initiated or any other idea how to proceed?