Customising VoiceOver Voice on Mac

Hi all,
I have been a Mac user for around 4 months now, so am still quite new to the whole thing. forgive me if this question therefore comes across as ill-informed.
After performing the two software upgrades I have so far come across (to 10.14, and then today to 10.14.1), my VoiceOver voice has reverted to the default, in my case Daniel. I have to open Voiceover utility, and change each content-type's voice back to my preferred voice, Ava, and yet these customisations only seem to last until I upgrade the software on my Mac, at which point everything is reverted back to Daniel. Is there a way of saving my VoiceOver customisations so that when I upgrade Mac OS, I don't have to go through this?

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