Steps to reproduce:

1. open a web page with Firefox or Chrome (browsers I tested);
2. start sayAll;
3. after some words or lines, stop it with control or shift;
4. change line with arrows or open a new page,;
5. relaunch sayAll.

Actual behavior:

SayAll reads a text chunk of previous reading before the new text.

Expected behavior:

SayAll forgot the old text and starts from new one.

System configuration

NVDA installed/portable/running from source:

Installed.

NVDA version:

NVDA version alpha-22126,ff79f518
(but it happens in last two-three alphas)

Windows version:

Windows 10 20H2 build 19042.870.

Name and version of other software in use when reproducing the issue:

Firefox 86.0.1, various voices/synthesizers (including OneCore).