The stale check is a plan asset, I don't see how you can reject it. I would request that the prior provider hand over whatever information I need to take care of the assets though.
I have had this happen before because some investment platforms have more than one step in a distribution. Basically the provider takes the amount from the plans account, and makes the payment from a provider account. As far as the plan can see, the payment "cleared" when removed from the plan account. On the provider side, the payment from their account goes stale so the amount remains in that account rather than being returned to the plan account.
This is one of the issues in the missing participant debate. It gets even more fun when you add overlapping plan years and withholding...