I am building an importer for a wordpress project and have to map blocks to other block types. Therefore, I have an abstract base Block-Class that looks like this:

abstract class Block
{
    abstract public function getBlockName(): string;

    abstract public function getBlockData(): array;

    public function getBlockAnchor(): ?string
    {
        return null;
    }

    public function getBlockMode(): string
    {
        return 'edit';
    }

    public function toArray(): array
    {
        $data = [
            'blockName' => $this->getBlockName(),
            'innerBlocks' => [],
            'innerHTML' => '',
            'innerContent' => [],
            'attrs' => [
                'id' => $this->getBlockAnchor(),
                'name' => $this->getBlockName(),
                'align' => '',
                'className' => '',
                'mode' => $this->getBlockMode(),
                'data' => $this->getBlockData()
            ],
        ];

        $data['attrs'] = array_filter($data['attrs'], fn($el) => !is_null($el));

        return $data;
    }
}

An example implementation of a small stage block looks like this:

class StageSmall extends Block {

    public function __construct(
        private string $headline = "",
        private string $copy = "",
    ) {}

    public function getBlockName() : string {
        return 'acf/stage-small';
    }

    public function getBlockData() : array {
        return [
            "stage_small_title_headline" => $this->headline,
            "_stage_small_title_headline" => "field_69bk817sdgsee3r2ll-Headline",
            "stage_small_copy" => $this->copy,
            "_stage_small_copy" => "field_667bd92e8feb6",
            ];
    }
}

And my mapping looks something like this (migrateOldBlockName does some mapping and returns an array of Block instances)

        $migratedBlocks = [];

        foreach($blocks as $block) {
            switch ($block['blockName']) {
                // ...
                case 'acf/old-block-name':
                    $migratedBlocks = [...$migratedBlocks, ...$this->migrateOldBlockName($block)];
                    break;
                // ...
            }
        }

        $migratedBlocks = array_map(fn($block) => $block->toArray(), $migratedBlocks);

        wp_insert_post(array(
            // ...
            'post_content' => serialize_blocks($migratedBlocks),
            // ...
        ));

When I now migrate HTML, for example the string <p class="h2">EXAMPLE TEXT</p>, it turns into u003cp class=u0022h2u0022u003eEXAMPLE TEXTu003c/pu003e. It seems like there are missing slashes, for example " should correctly be stored as u0022 in the DB, but it is u0022. If I use wp_slash($this->getBlockData()) in the Block class, the quotes are correctly transformed, but the remaining characters are still broken and it throws an exception if I try save fields that contain single quotes.

What is the correct way to parse the block data strings so that they get rendered in the correct format?