Summary block error when reloading post

Hello!
First, thanks for this great plugin.
I heavily use the summary block in my site. However, there’s a small problem with the block.
This block can be inserted into post and works well. But, the next time I reload the post to edit, this block always shows a notification “This block contains unexpected or invalid contents”. The developer console (chrome) shows an error “Block validation: Block validation failed for advgb/summary“:
Expected:

<ul class=”wp-block-advgb-summary advgb-toc alignnone”><li class=”toc-level-1″ style=”margin-left:20px”>A header goes here<li class=”toc-level-1″ style=”margin-left:20px”>A header goes here

Actual:

<div class=”wp-block-advgb-summary alignnone”><div class=”advgb-toc-header collapsed”>N?i dung</div><ul class=”advgb-toc alignnone” style=”display:none”><li class=”toc-level-1″ style=”margin-left:20px”>A header goes here<li class=”toc-level-1″ style=”margin-left:20px”>A header goes here</div>