Believe it or not (you probably do!!) I've had the same problem trying to list cutting discs for an angle grinder.

I got around it by listing it with age varified delivery but in the listing informed buyers that it will be delivered by "normal" parcel post. This is the item no 297475739248. I even deleted the word blade from the listing but it still failed. My guess is it's picking up the word "cutting"

Although one can't argue about selling bladed items without age verification delivery eBay have made a real mess of applying the rules as they obviously capture wrong items. This is a real pain as age verification delivery will put a lot of buyers off due to the fact they have to be at home to receive the parcel.

Another example of eBay at it's finest.