I’m seeing this same behavior. But it doesn’t work even after I remove the minimum rows requirement.
EDIT: After I remove the minimum rows requirement, I can rearrange the blocks with the exception of the first block. It always remains first.
Here’s what the POST to admin_ajax.php looks like. For some reason, the first item has a [0] array key but the subsequent items appear to have hashed keys.
action: acf/ajax/render_block_preview
block[id]: block_5c5a09cdd6c41
block[data][field_5c59f6ad04f2e][0][field_5c59f6ad0803b]: 4955
block[data][field_5c59f6ad04f2e][0][field_5c59f745b0c76]: The Distillers League of Alabama logo
block[data][field_5c59f6ad04f2e][0][field_5c59f6ad08084]: #f4f4f4
block[data][field_5c59f6ad04f2e][5c5a09ead6c42][field_5c59f6ad0803b]: 4953
block[data][field_5c59f6ad04f2e][5c5a09ead6c42][field_5c59f745b0c76]: Shoal Creek logo
block[data][field_5c59f6ad04f2e][5c5a09ead6c42][field_5c59f6ad08084]: #a6a5a5
block[data][field_5c59f6ad04f2e][5c5a0a03d6c43][field_5c59f6ad0803b]: 4945
block[data][field_5c59f6ad04f2e][5c5a0a03d6c43][field_5c59f745b0c76]: Attune Health logo
block[data][field_5c59f6ad04f2e][5c5a0a03d6c43][field_5c59f6ad08084]: #aaad00
block[data][field_5c59f6ad04f2e][5c5a0a5ed6c44][field_5c59f6ad0803b]: 4876
block[data][field_5c59f6ad04f2e][5c5a0a5ed6c44][field_5c59f745b0c76]: America's First Financial logo
block[data][field_5c59f6ad04f2e][5c5a0a5ed6c44][field_5c59f6ad08084]: #ffffff
block[name]: acf/logo-grid-block
block[align]:
block[mode]: preview
nonce: 057b20ab19
post_id: 4974
