No, I did not get a resolution.
At the moment I am using a work around where if I want to debug the parts of the code that do http requests I run a single threaded version of the script, and if I want to debug the threading stuff, I comment out the http stuff and replace it with dummy placeholder code.
It would be nice to know where the bug lies so that I can report it to the correct place, though seeing as LWP is core, perhaps I should just report it as a bug against perl, and not concern myself with which module is to blame.