Content Templater causes serious error

Greetings, and Merry Christmas!

We are today no longer able to edit or create articles on our site, due to whatever this error message means:

RegularLabs\Library\HtmlTag::flattenAttributes(): Argument #1 ($attributes) must be of type array, stdClass given, called in ******/plugins/editors-xtd/contenttemplater/contenttemplater.php on line 161

(Both Joomla and all our Regular Labs extensions are up to date. I have also tried to reinstall the extension.)

Thank you!

I tried it now, and the error is history.