I have an extensive background with phpBB and various other open-sourced platforms of similar nature. One thing that you didn't mention on your job request was which database back-end your instance of phpBB is using. I can assure you that I can work with any case, be it MySQL, MS SQL, PostgreSQL; however you have it set up. For the very reasonable total cost of $20, I will identify the errors plaguing your forum and fix them in a matter of hours, given sufficient temporary access to your hosting platform.
Thank you, I hope to hear from you soon.