I'll be very quick.
I think it happens quite often that the clerk invites witnesses and they decline the invitation, which complicates things quite a bit. We often call or contact her, and she tells us roughly where things stand. I understand that it's sometimes difficult to predict. For example, on Thursday, one of the witnesses I had proposed to invite initially refused, and then there was talk of possibly postponing their appearance.
You could send us information telling us that you're trying to invite witnesses. I'm aware that this would complicate your work. In any case, we'll see what can be done. I understand that it's difficult. That said, if we had decided on the studies more in advance, it would be easier.