Tom, this isn't something I've encountered and I'm a regular user of Brave.
What voice are you using? If Eloquence, are you using the Reed voice or one of the other variations?
What parameters are you using, as in the settings for pitch and rate?
Is this behavior consistent? In other words, if you perform a "say all" three times on the same page will it exhibit the same behavior on the same text all three times?
Can you provide a specific URL where you notice this behavior and specific text areas where the voice changes?
With this information we can try to see if we can reproduce the issue.
By chance I'm wondering if the "indicate capitalization" option in Settings Center got changed. To verify this,
1: Ensure that Brave is open and that it is the active window.
2. Press insert-6 (on the numbers row) to open Settings Center.
3. Type "cap" without the quotes.
4. Arrow down to the "indicate capitalization" setting and ensure that it is set for "char (meaning character.)

David Goldfield,
Blindness Assistive Technology Specialist
JAWS Certified, 2019

WWW.DavidGoldfield.org

I am having a problem with the "say all" command in the latest version 2021 of Jaws. Using the Brave Web browser, Random words are spoken with a rising pitch, like capitalized letters are. At times it occurs every few words and is very annoying. A friend looked at the screen an could not see any thing that would cause this. It doesn't happen with IE or Edge. Does anyone else have this problem or a cure.  Tom