This bug (2425277) was discovered after the completion of the 5.0.20 release.

When Account Data Upload (ADU) loads a new SG pledge with a payment and the previous SG was a charge that became a CK due to the number of charge rejects, the new pledge will have a blank date last pulled. This means it can be pulled again as soon as Charge Processing runs. The intended behavior is that since the pledge was loaded with a payment, the date last pulled is set to the gift date. One possible workaround would be to upload the payments separately from the pledges.