In short we don't know. Legal records from these societies are quite frankly non-existent. There are law codes that have survived, notably in the case of something like the Laws of Æthelberht, but nothing in the way of decisions, court cases, or the aftermath of legal proceedings. All that we can say with certainty is what is written in the law codes, but we cannot say with certainty what the day to day execution of these laws was, much less what might have happened in instances that were not covered in these law codes. So there are no clear cut examples of a family or person who continued their legal vendetta after the payment of satisfactory wergeld, but that is largely due to the lack of solid legal documents from this time period, assuming any such documents ever actually even existed.

For example, the Laws of Æthelberht do not include guidelines on what to do if the restitution is given and the grieved party or family still enacts vengeance. Neither do many other Anglo-Saxon law codes such as those set forth by Alfred in Wessex or Edward. Indeed if payment is made, and it is the full and lawful amount, then the issue is settled. Any further actions would be criminal and subject to their own fines.

There are literary examples of wergeld payments, and perhaps it is unfair, but I do not think that they are worthwhile in examining for these issues. The literature that invokes the wergeld payments is often from a period some centuries later than the events being described, and I do not think that they should bear the weight of being treated as factual accountings of legal matters. More "contemporary" literary works such as Beowulf do not really concern themselves greatly with wergeld payments, though it is remarked that Grendel does not offer compensation for his bloodlust, for obvious reasons, he was not forth coming with payment.

Now there is an interesting section to the poem later on that describes the state of Hrothgar's kingdom after Beowulf's departure that deals with vengeance being taken for the slaying of a kinsman, but it does not deal with wergeld specifically. If you'd like me to follow up on it though, I'd be happy to.