vam2017

Fine. Thank you so much!
Updated the plugin as you said. Everything is working well.
Below is the working code:

[mla_tag_cloud]
taxonomy=attachment_tag 
mla_link_href="[+page_url+]?current_id={+term_id+}"
number=0 smallest=12 largest=12 separator=' / '
[/mla_tag_cloud]

[mla_gallery] 
attachment_category=mygallery
tax_query= "{+template:(array \\( 0 => array \\( 'taxonomy' => 'attachment_tag', 'field' => 'id', 'terms' => array\\( {+request:current_id+} \\) \\) \\))+}"
post_parent=all
mla_caption="{+image_alt+}" 
columns=3 posts_per_page=4 size=full link=file 
mla_link_class="nav-links"
[/mla_gallery]

[mla_gallery]
attachment_category=mygallery
mla_output="paginate_links,prev_next"
mla_link_class="nav-links"
tax_query= "{+template:(array \\( 0 => array \\( 'taxonomy' => 'attachment_tag', 'field' => 'id', 'terms' => array\\( {+request:current_id+} \\) \\) \\))+}"
post_parent=all
columns=3 posts_per_page=4 size=full link=file
[/mla_gallery]