Spoken Content screen reader voice changes on its own

I occasionally use Mac's built-in screen reader for long blocks of text. Ever since I have updated to the new Sonoma OS, when the reader is in the middle of reading aloud to me, it will switch voices on its own. I have the voice set to English (India) Siri (Voice 1) in my settings, and that never changes, even when the sound coming out does change. The voice it always changes to is English (US) Samantha. I've not been able to catch this on any recordings as the reader can go tens of thousands of words without switching & is completely unpredictable, aside from never interrupting a word or sentence in the middle. Once it changes, even if I stop the reader and have it speak the same selected text over, it does not change at the same spot in the text again, so there is nothing within the text causing it to change. Is there any way to stop this that anyone knows of?