Since this behavior does not happen each time a VoiceOver Announcement/flash message appears, it's a tough bug to solve. I've had notifications from the same app freeze the braille display and phone in one instance and not the other. It also seems to happen to some people far more than others.
Steps to reproduce
Receive several notifications with VoiceOver AnnouncementsFlash Messages turned on. It will eventually happen
Disable VoiceOver Announcements/Flash Messages. This can be done by going to settings>Accessibility>VoiceOver>braille>Braille ALert Messages, and select the "off" option. Note that this disables all messages, so you will not get any sort of notifications that jump up on the braille display. Space with n, which will allow you to view the Alert Message history does not allow you to view these messages when the feature is turned off. Alternatively, you could also set your iOS device to Do Not Disturb. Once the issue occurs, it appears the only fix is to press the volume up, then volume down button and press and hold the side button to reset the iOS or iPad OS device.
I've also experienced this
I've seen this on an SE2020 and an iPhone 13 running 15.2, both using a Brailliant BI20X. Very annoying indeed as I did find it handy to reply to whatsApp messages etc. while reading a book or the paper.
I would call apple accessibility. If they reproduce it there hopefully it will be fixed quick.
I’ve seen this with my focus 40, 5th generation
I’ve seen this while using my focus 40, 5th generation with my iPad, which is running the beta of iPadOS 15.3.
This bug makes using a braille display with an Apple device, nearly impossible.
There is a possible fix for this issue. Go to the braille settings under Voiceover settings and turn off braille alert messages. This has fixed this issue for some people.
I've seen this too
I've also seen this happen with an iPhone 13 and a focus 14 forth gen display. I turned off the braille alert messages, and that fixed the problem but I feel this is a bug that needs to be fixed. I hope apple can get it fixed soon.
I also have experienced this
I have the braille alerts turned off. I have also called Apple Accessibility. All we can do is wait for the bug to be fixed. I have also noticed with certain braille displays (Focus in particular) that will just randomly start jumping and won't stop. Some people have said that their Mantis displays are doing the same thing. I'm using a BI20X right now. It's an okay backup! But the Focus usually works much better. I hope with 15.3 out, that the bug will be fixed.