After 5 or 6 Naida changed on a quasi-monthly rate since March 2014 (and very fortunately, I live in the same town where is the distributor!) - at last! - I got the redesigned one, and now it is going fine for one month the next Monday; on every Monday, I'm inspecting he "window" with microscope, finding it clean as in 1st day, left apart some grains of dust.
The previous design was regularly filled by liquids pushed by capillarity, and the colors of residuals were repellent, to say little...
The window added in the new design definitely breaks the capillarity matter.
Also, they put some silicone beneath the top part, that which is covering the buttons; in the previous design, if I sucked in the groove, there was often fluids spilling.
Now, nothing.
On the other hand, I customized a bit my batteries by rounding edges with a nail file, thus opening a bit the originally narrow groove that forms the closure, so that the above part (i.e., processor case) behaves like a gutter, and thus keeping internal parts safer from flowing sweat.
Let's Hope!