Why custom search URL not saving?

Hi all,

Having a bit of an annoyance with a custom search engine URL (Brave for Mac OS).

Bought a new computer, installed Brave, created my custom search engine and saved the custom URL. Except I made a mistake with the URL so I went in again to save the correct one. Come next morning, Brave reverted to the original/incorrect URL. Fixed again, and next morning, reverted again.

Can you help? Perhaps I can edit the source file where these URLs are stored (which file? Location?) or how can I persuade Brave to store the URL for good?

Thanks!!

Pete