I am happy to report that I finally got 3.9 to install.
I can't say for sure what the actual issue was, though I suspect files were getting corrupted somewhere in the process.
Steps,
disable windows defender
run BSG launcher as admin
integrity check ----> Fail
repair
run SPT installer as admin
I have tried this multiple times before along with various combinations of copying files manually and nothing worked until now and I have no idea why.