Yevamos 104b - Chalitzah for one who can't hear

The gemara says that if either the yaveim or yevama cannot speak they cannot do chalitzah since one has to at least be fit for kriah. The Rashash discusses one who cannot hear but can speak, so she is technically fit for kriah, but it is impossible for the dayanim to teach her what to say (that is his case), so she won't be saying anything, is the chalitzah valid? He suggests that if the dayanaim cannot teach her what to say, she is not fit for kriah and the chalitzah would not be valid (he then goes on to deal with the shayla from a different perspective). The Ramban says that if the yaveim or Yevama is deaf but they can speak, they cannot do chalitzah since the beis din cannot fulfill the "v'koru lo" (the Ritva says a little differently that the yaveim and yevama have to be able to hear each other). The Ramban approach is different from the Rashash in that the Ramban seems to understand that the obligation of the Beis Din is to actually teach them what to say, not just that they should be fit for kriah. If the Beis Din taught them what to say and then she becomes deaf, R' Ahron Yafen understands that this would be okay according to the Ramban even if she did not actually do kriah (even if she forgot what to say, since the beis din fulfilled the obligation to teach them what to say), but based on the Rashash it would not be okay if at the time when the kriah should be done, she forgot what to say and is not fit for kriah.