backdrop cms module-created blocks deltas not working - module

Question

(tagging with drupal7 because i cannot create a tag for backdrop)
i have a fresh backdrop install, with a new theme duped from bartik, and a new layout duped from moscone_flipped. no code changes to those yet.
i have a module that creates 2 simple blocks, mostly just some html. i have implemented hook_block_info() and hook_block_view(). i can place blocks into regions in the layout using the admin ui. i can see each block on the front end page when i place either one of them. but not both. when i have both blocks placed in the layout, for some reason both regions display the output from the same block. and i have verified that it is always the first block defined in the array returned from hook_block_info(). i have cleared caches, checked code, etc.
has anyone seen this before?
btw, i just applied the recent security upgrade, and the behavior is the same both before and after the upgrade.
i will paste in the module code below, in case i have missed something.
thanks for any help anyone can provide.
// implements hook_block_info()
function mbr_block_info()
{
$info = array();
$info['rate-tables'] = array(
'info' => 'Rate Tables (Buttons)',
'description' => 'The displays the rate table links for the sidebar',
);
$info['mbr-footer'] = array(
'info' => 'MBR Footer',
'description' => 'Displays footer links, disclaimer, copyright',
);
return($info);
}
// implements hook_block_view()
function mbr_block_view($delta = '', $settings = array(), $contexts = array())
{
$block = array();
switch($delta)
{
case 'mbr-footer':
$subject = null;
$mbrFooter = getMBRFooterBlock();
$block = array('subject' => $subject, 'content' => $mbrFooter);
case 'rate-tables':
$subject = null;
$rateTables = getRateTablesBlock();
$block = array('subject' => $subject, 'content' => $rateTables);
}
return($block);
}