Interactive book with fill in the blanks and drag the words

In 2022, I created a relatively complex and multi-part course as an ‘interactive book’ that I would now like to offer again. When updating some content, I received the following error message when saving: ‘count(): Argument #1 ($value) must be of type Countable|array, null given’.

While searching for the cause of the error, I first noticed that the question types ‘fill in the blanks’ and ‘drag the words’ were apparently responsible. I also noticed that both types are no longer part of the ‘interactive book’. Since when and for what reasons were they deleted? Or is the problem with my moodle?

Remarkably, the question types work without any problems in the unmodified book, only when saving does the error message appear. Is there a solution to this?

I will ask my administrator about the version of moodle and possible updates. But maybe the solution is already known.