Error loading block: Invalid parameter(s): attributes

Hey! Thank you for creating this fine block for WordPress. It’s just what we need, a simple block for a TOC without countless bells and whistles.

I’m testing it on a site, running WP 6.4.1 and PHP 8.1, and in the block editor, I get the error Error loading block: Invalid parameter(s): attributes

Inspecting the error, there are some more hints.

XHRGET
https://removed/wp-json/wp/v2/block-renderer/simpletoc/toc?context=edit&attributes[no_title]=false&attributes[title_level]=2&attributes[title_text]=Table of Contents&attributes[use_ol]=false&attributes[remove_indent]=false&attributes[add_smooth]=false&attributes[use_absolute_urls]=false&attributes[max_level]=2&attributes[min_level]=1&attributes[accordion]=false&attributes[wrapper]=false&attributes[bmCSS]=&post_id=2800&_locale=user
[HTTP/3 400  135ms]

	
code	"rest_invalid_param"
message	"Invalid parameter(s): attributes"
data	Object { status: 400, params: {…}, details: {…} }
status	400
params	Object { attributes: "bmCSS is not a valid property of Object." }
attributes	"bmCSS is not a valid property of Object."
details	Object { attributes: {…} }
attributes	Object { code: "rest_additional_properties_forbidden", message: "bmCSS is not a valid property of Object.", data: null }
code	"rest_additional_properties_forbidden"
message	"bmCSS is not a valid property of Object."
data	null

Any idea what might cause this?

The fun part is, that the block renders the TOC just fine on the front end 🙂

Please let me know if I can do anything to help troubleshooting this issue.
Bjarne