Clearly, there are some bugs involved in all this, most likely in YEM itself, but to my mind the underlying problem is the complexity of the situation as a whole -- that YEM is so weirdly designed, and has such a counter-intuitive user interface, along with an almost complete absence of useful documentation (not to mention the lack of an authoritative truly helpful instructional video from Yamaha). Given this perfect storm of oddities, errors, and omissions, it's challenging even to identify which problems are coming from possible bugs, and which are due to poor design, non-standard GUI, or user error.
In fairness, one can hardly consider these reported difficulties simply as user error when it's so difficult to explain YEM's unusual use cases in the first place! I shudder to think of all those Genos owners who don't visit discussion groups like this one, and who may well have only marginal expertise at their local keyboard store. Or the third-party developers who have to support their customers with very limited resources, while trying to sell their products to a market that's already having problems installing things.
Realistically, these issues probably span multiple departments at Yamaha. The seriously expert developers who designed generations of Arranger UI's, and the intensely technical developers who wrote the elaborate firmware inside generations of Arrangers, obviously didn't create YEM. Or if they did, certainly not as a consumer product (perhaps as a quick file transfer utility that wasn't originally conceived as a critical tool for thousands of users).
But the will to fix all this will require mandate and funding from an overarching layer of Yamaha admin, and that's where Marketing comes into play. So it's a bit of a strategic mess for us users, and we really need to get the right feedback to the right levels of Yamaha management. They're rightfully proud of their position in the musical instrument industry, and this YEM situation should be deeply embarrassing to someone at Yamaha with major clout.
Allen