VoiceOver can sometimes become sluggish when adding or editing a Rotor voice. While the full presentation of this behavior is inconsistent, this issue can reliably be reproduced when adding or editing one's Personal Voice for use with VoiceOver; and it can sometimes be reproduced with other voices as well.
1. Navigate to Settings> VoiceOver> Speech> Add Rotor Voice.
2. Navigate to a voice of your choosing and double-tap to activate it. (Note that you will need to download the selected voice if you have not already done so previously.)
3. On the screen to edit the voice, VoiceOver will sometimes become slower to respond.
Note that the delay in responsiveness can also occur when editing voices already added to the Rotor as well.
The only workaround we are aware of for this issue is to adjust speech rate and other settings through the Rotor, when available.