This seems to be an ongoing issue at 4.13 and 4.2 or just generally 4.x. The solution points to synch issues but even if the cluster shows no replciaiton issues it cna still occur. It seems that the only solution is per phone in that you manually turn it off, on , off again, also it is not every phone so tracking it down and replicating the fault when it occured on my site was not easy