Why is Safari with VoiceOver dropping messages from live region updates?

Running Mojave. I have a webpage, that wants to announce something to the user. I found that when it happens, VoiceOver is stuck explaining where the focus is and "forgets" to announce the live region update. Our workaround is to set a timeout to update the live region where it is likely to not have any distractions, but this feels hacky and not following what I learned an assertive or polite live region should do.


We also noticed this not working on Mojave, but working better on High Sierra.


Thoughts on why that's the case, or what we can do to effectively use the live region without timeouts?


Thanks!