Take some teflon tape and twist it into a string. dig out what is left of the twine and replace with the teflon string. I would ( and did) get some teflon tread sealing paste and put that on the threads as well ..... had no leaks!

Teflon tape, rather than paste, might help on the threads but the threads are a bit fine for it in my view. If you can, get the paste that is approved for Gasoline etc. but honestly I personally doubt there is much, if any, difference. We are not taking about high pressure here!

If all else fails, just remember that all oil leaks eventually stop.