BuddyPress.org

I can call a custom template for my custom page like so:

function my_new_group_show_screen_content() {
echo bp_buffer_template_part( 'groups/group-custom', null, false );
}

Then, just for testing, on that template, I record a visit to that page as an activity, like so:

$defaults = array(
'user_id' => '1',
'action' => 'A user just…[Read more]

Is the second file is overloaded? & Overloading & copying it over from:
/bp-templates/bp-legacy/buddypress/

It may be?

you need to debug a bit, try deactivating plugins and change themes to verify those are not causing the problem.

Are you running a cache on the site?