Laravel "whereHas" anded with "where" causing "where" to be ignored

I have the following code snippet for retrieving requests made by a user , here I need to apply 2 filters

1. A mandatory filter for restricting items requested by logged in user (line # 2).

2. An optional set of filters based on keywords entered by the user (inside the if ($keywords) branch).

It's working fine if $keywords is empty (user hasn't entered anything), however, when $keywords has something, the first mandatory user query is totally ignored and only what's inside the branch gets executed, . the strange things is that inside the branch I'm reusing the filtered set already ($requestItems = $requestItems->whereHas)

In a nutshell, whereHas is causing where to be ignored although the queries are connected together!

$keywords = request()->get('keywords');
$requestItems = RequestItem::where('requestor_id', '=', Auth::id());

if ($keywords) {
  $requestItems = $requestItems->whereHas('relParentRequest', function($query) use ($keywords) {
      $query->where('display_name', '=', $keywords);
  })->orWhereHas('relService', function($query) use ($keywords) {
      $query->where('name', 'like', "%$keywords%");
  })->orWhereHas('relEntityState', function($query) use ($keywords) {
      $query->where('name', 'like', "%$keywords%");
  })->orWhereHas('relRequestor', function($query) use ($keywords) {
      $query->where('name', 'like', "%$keywords%");
  })->orWhere('display_name', '=', $keywords
  )->orWhere('created_at', 'like', "%$keywords%");
}
$requestItems = $requestItems->paginate(10);

via Chebli Mohamed