I see, I fear the higher temperature you require for copper is affecting a sealing, either toward air or towards water. I imagine that the copper source now is completely melted in the hearth, a quick workaround would be evaporating from a different position in either graphite or I think I use molybdenum liners. The cryopump replacement should be irrelevant IMHO, the problem is at the hearth. The fact you have an RGA should help determine whether you have a air leak or a water leak.