IIS not giving line numbers in stack trace even though pdb present

Question

Web config has debug=true and the project is a debug build and the pdb files are present in the bin directory, but I do not get line numbers in my stacktrace when an excepti

Answer 1

It turns out using impersonation with the web.config:

causes the loss of the line numbers in the stacktrace. I took the entry out and my line numbers returned, put it back and after a few hours (Kerberos ticket refreshing?) the line numbers disappeared again.

Not sure why impersonation affects the stack trace but it does - would be happy to have someone confirm / explain this...