Right now excludedBlocks is a hard coded list. Some plugins dont like having the additional openPopupId added in and will cause a 400 api error.

In my case, it is gravity forms doing this. I manually changed excludedBlocks to var excludedBlocks = ['core/nextpage', 'gravityforms/form'];

There should be a php filter to output with ex pum_block_editor_vars to dynamically add compatibility with different plugins.

Thanks :)