Create gallery in a reusable Gutenberg block

Hello,
there is very little information, this error can occur for a thousand reasons. Especially if you create new blocks in the reusable block. The maximum I personally do is add the block to Reusable block. But as I understand it, you went further in these unpredictable combinations.

But it seems to me that you get the error when you click Update post / page button – then this is a completely different story, which does not apply to Reusable blocks