This is not directly related to VsCode based debugging but it might nudge you in the right direction.

I am using Webstorm to debug and I was facing the same issue there. Then I went to the debugger configuration of my project(Edit configuration page) and saw that the "Ensure breakpoints are detected when loading scripts" was enabled. After disabling it and restarting the debugger it fixed the issue.

Note: on first load of a debugger, it will always show the sources tab when you open the deb tool. After switching to a different tab, the steps I described above fixes the redirection to source tab on each page reload.

My suggestion is that you look for such a configuration in VsCode and check if there is similar setting that is enabled there. The configuration might not be a UI based thing rather might be a JSON file(as most things are in VsCode).