Ok.
First of all, thank you for files for test.
I saw now that you are using a lot of rex files which are Drums.
I don't know WHY they do that , but in Drums, each key has a waveform attached. In other types of voices, an element is a waveform.
So think about that for a normal voice you can use maximum of 8 waveforms, but for drums you use A LOT. That's why you reached so quickly the limit!
Unfortunately, I cannot do anything in this case.
Even if I remove those empty waveforms in drums (un-assigned keys) the number of waveforms is big.
I see only one solution here: Drums to be created exactly like normal voices (not by you, but Yamaha to create in the same way the file), which I think will never be done
Edited:
Or two: the number of waveforms to be increased to a bigger one, thru a software/firmware update.
PS: If you find a solution to reduce the number of Drums files in your imported files, you can use your content, otherwise it will be a problem for you!
As a suggestion: If you use the same key/note/sound in your all drums, don't import them in all, use the sound in only one drum and open DrumSetup to get the needed sound from the drum which has needed sound! In this way, you will free up some of the waveforms. For example, cowbell sound, you can find it in a lot of drums in keyboard, or other percussion sounds, too
Best regards,
Vali