It's not a problem with the tuning. The problem is that the old UE900 had a weakness that the shells would tend to fall apart at the join, and the MMCX connectors would oxidise. The new UE900s being sold in Japan have an improved weld and an improved connector design. Worse still there are numerous examples in this thread where the shells fell apart and Logitech UE was aware there was a tendency for this to happen, but they did not consistently offer to repair or replace the product for customers. Despite them being AWARE of the fault and fixing it with a new revision.
People will order the UE900s in other markets thinking they are getting an improvement, and when they aren't they will contact CS which seemingly has no idea about what is going on. Customers should know what they will actually be getting in the box when they order it.