Hi @GavinA1970
The simpleset way is to break the while loop after you render the image like so:
<?php while( has_sub_field('project_images') ): ?>
<?php $firstimage = wp_get_attachment_image_src(get_sub_field('project_image'), 'full'); ?>
<img src="<?php echo $firstimage[0]; ?>" alt="" style="display: none;" class="fp_preview" />
<?php break; ?>
<?php endwhile; ?>
That will break out of the nested loop and continue the previous loop.
Hope that helps.
Thanks
E