In both cases the error occurs with PHP 8.0.x or 8.1.x.
FYI: I run the forum using PHP version 8.1 and it works. Today, I updated the template and checked the mail function. All mails were received, without an error. I also try PHP 8.2 and it works.
Maybe the error, i.e., not saving entries of registered users, is also related to the mail function (sending notification mail)?!
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