I suppose there is a copy-paste fail

./api/classes/Chost.php
In a function massRemove:

if (isset($data['templateids_clear'])) {
$options = array(
'templateids' => $hostids,
'templateids_clear' => zbx_toArray($data['templateids_clear'])

Note:
'templateids' => $hostids,
but probably should be:
'hostids' => $hostids,

Also please add an option 'templateids_clear' to the function description (PHP doc)