invalidate the block cache

I am able to fix this in a preprocess hook but I think it should be fixed in the module itself.

Here is what I used in my preprocess hook

/**
* Implements hook_preprocess_HOOK() for block.html.twig.
*/
function themename_preprocess_block(&$vars) {
if($vars['plugin_id'] == 'your-block-id') {
//-- This sets the block cache to 6 hours.
$vars['#cache']['max-age'] = 21600;
}
}