This situation has so far only occurred with the Samsung Galaxy Nexus.

It seems like an issue with the phone itself but we have been informed that a pending software update may be able to resolve the issue. Unfortunately this is something out of our control and the phone should be successfully unlocked, but the only advice we can offer is to avoid turning the phone off as much as possible.

We do understand that it can be an annoyance but we expect that the software update will remove the need to enter the code altogether once it has been applied.