使用Ajax表单的Zend Framework 3中的CSRF问题

I am having an intermittent problem with the CSRF element in a ZF3 ajax form. I am using the following to configure the element

$this->add([
     'type' => Element\Csrf::class,
     'name' => 'onlineGameCsrf',
     'options' => [
         'csrf_options' => [
             'timeout' => 600,
         ],
     ],
 ]);

and including in the form using

echo $this->formRow($form->get('onlineGameCsrf'));

Most of the time this works as it should but every so often, maybe one in ten times, it fails. The logs show the following error.

[notSame] => The form submitted did not originate from the expected site

I have tried a couple of 'fixes' that I have found on SO and elsewhere. The first was moving $form->prepare() to the view file and another was to increase the timeout in the configuration. Neither of these worked, though perhaps I wasn't increasing the timeout enough (I went to a max of 2000).

I am using the same CSRF element elsewhere in the site on non-ajax forms and it is working correctly with no issues.

Any help would be much appreciated.

Thanks.