GroupedList SQL Error

Silverstripe Version: 3.7.1

Question: re: I’m getting a SQL error when using GroupedList

This is the tip of my trace; the SQL error I get when trying to use the GroupedBy function of GroupedList

DBConnector->databaseError(You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ‘AS “1” FROM “SupportService” WHERE (“SupportService”.“PageID” = ?)’ at line 1,256,SELECT DISTINCT AS “1” FROM “SupportService” WHERE (“SupportService”.“PageID” = ?),Array)

My controller function
public function Services()
    $services = SupportService::get()->filter([
      'PageID' => $this->ID

    return GroupedList::create($services);

My model defines a grouping function
public function getCategory()
  return $this->getField('Category');

My view template
<% loop Services.GroupedBy(Category) %>
        <% loop $Children %>
        <% end_loop %>
<% end_loop %>

Any ideas?