After securing a NPC village with a fence my son killed a pillager captain 50 blocks from the village perimeter and got the bad omen effect. Sure enough, we returned to our village anyway... But now we've gone through at least 12 consecutive raids since, and according to the Minecraft Wiki we should only expect 7 raids on hard. Is this a possible bug? 

Edit: worth mentioning - after a few waves of raids we moved our village bell to a different spot in our village...