Conflict between with a function in two different modules
Rather than module weighting, I would suggest using hook_module_implements_alter to ensure your hook gets run last. So, something like this:

function hook_module_implements_alter(&amp;$implementations, $hook) {
  if ($hook == 'theme_registry_alter') {
    $group = $implementations['my_module'];
    unset($implementations['my_module']);
    $implementations['my_module'] = $group;
  }
}