[Error Code] Bizhub C500 error code SC29-07

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I did a full maintenance on the c500 however i didn't replaced the yellow developer because a new developer unit and developer was replaced 50,000 prints before the maintenance because it was dumping. The copier worked fine for about a week and 4000 prints later it gave a sc45-20 error code which when reset the copier gives a sc29-07.
I would like to know if any one have ever experience this problem and what are possible the fix before i pour a new developer.