NVDA reads input validation message twice

[Kombat-Wombat]

Note:
I noticed a similar issue in another website, but it seems to be a duplicate problem as this page:
angular/components#14281
and it seems to be particular to NVDA compared to JAWS for example.
Input validation messages that are created after a field is left can be read off twice instead of once.

Steps to reproduce:

Launch NVDA
Go to https://stackblitz.com/angular/brleoyyorkap?file=app%2Finput-error-state-matcher-example.ts
Input some text so the input validation message appears

Actual behavior:

The error message is read twice

Expected behavior:

The error message is read once

System configuration

NVDA installed/portable/running from source:

I just ran the one from here:
https://www.nvaccess.org/download/

NVDA version:

2021.1

Windows version:

Windows 10 Enterprise

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

stackblitz

Other information about your system:

Other questions

Does the issue still occur after restarting your computer?

yes

Have you tried any other versions of NVDA? If so, please report their behaviors.

no

If add-ons are disabled, is your problem still occurring?

I don't think this is relevant

Does the issue still occur after you run the COM Registration Fixing Tool in NVDA's tools menu?

yes

[feerrenrut]

To ensure this isn't a bug in angular, could you please create a minimal HTML sample to demonstrate the issue. This will still require us to determine if the bug is in the HTML sample, the browser, or NVDA, but it removes one layer from the stack.