Description
When using conversation view, aka message threads in Mail, there are issues when you swipe to a new mail in a thread.
If there were four emails in the thread for example, and you receive a fifth. When you open the thread, you can use the up and down swipes in the messages rotor to go through messages 1 of 5, 2 of 5, 3 of 5 and 4 of 5.
However when you swipe down again, instead of hearing 5 of 5, VoiceOver goes silent.
You may find the message by tapping the middle of the screen, but navigation back up through the thread can then become problematic.
Steps to reproduce
Enable VoiceOver.
Enable conversation view in Mail.
Open an existing conversation thread that has received a new email.
Use the Messages item in the rotor to navigate to the new email at the bottom of the thread.
VoiceOver remains silent when you get to the new email.
Tap the centre of the screen to find the new message, though you may not land at the top, and still get no confirmation that it is the correct message until you engage the rotor again.
Then swiping back up, you can have further navigation issues.
Workaround
Tap the centre of the screen after VoiceOver has gone silent. Further left right swipes may be required to find the top of the message.
Alternatively, in the mailbox, select the Expand Message Thread option from the actions rotor and engage with the conversation that way instead.