Brave not working with phpBB forum software

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1

Description of the issue:
How can this issue be reproduced?

  1. Go to https://bogleheads.org/forum and register using a non-Brave browser

  2. Once registered, try to log in

  3. It doesn’t matter if shields are up or down for the error to occur.

Expected result: Instead of login, you get an error about the form submission.

Brave Version( check About Brave): 1.89.145

Additional Information: This started when the site updated their forum software to phpBB 3.3.16. I can use Safari to log in, but not Brave.