I just noticed that the credit/month in attached link is negative for computers 3 & 4:

https://boincstats.com/en/stats/-1/host/list/0/0/cca4389e86e7d4bacc618b873dae5f5d

However, if I go to BU's site, it shows the correct values for their projects, which is most of the points:
http://www.bitcoinutopia.net/bitcoinutopia/hosts_user.php?sort=rpc_time&rev=0&show_all=1&userid=6875

As one specific case, I'm not sure why on 2017-05-22, I lost 3,394,914,408 points:
https://boincstats.com/en/stats/-1/host/detail/304778401/lastDays

Any help would be greatly appreciated.

Thanks to the BOINC team. I see the credit has been fixed today for both computers.