Sounds like a bugged crawler, it should only be crawling a website every now and then, not daily, and if daily it doesn't need to download the entirety of the forum contents, normally crawlers are only interested in the html wording, cause pictures and videos they can link to and not have to actually download it.
When a google bot enters the forums I have or websites it barely registers any traffic since it keeps only downloading htmls and such.
Also, what the hell does it have to download on the forum in gigabytes? 90% of the pictures are links to outside resources. and vids are all outside resources.