Hi @homax
I think the issue is the wp_reset_postdata() is reseting the global query back to something other than the expected ‘category posts’.
I would modify your code to not use the wp_reset_postdata() function. You can do this like so:
<?php $posts = get_field('myfieldname');
if( $posts ): ?>
<?php foreach( $posts as $p): ?>
<?php echo get_the_title( $p->ID ); ?>
<?php endforeach; ?>
<?php endif; ?>
