Not real random function in a Blogger widget, it always shows 'neighbor' posts from the past

My blog is 12 years old, I have more than 5000 posts. I am using a widget that shows random posts from a specific label. I set it to show 2 posts in the sidebar, and I noticed that these posts are always 'neighbors', which means they are always from the same month in the past. For example, it's always 2 posts from May 2014, or June 2018. It's never something like: 1 post from May 2014 and the other from June 2018. Do you have any idea what the problem is? Here is the part of the code which (I believe) contains the mistake:

rand=Math.floor((Math.random()*_vRiO.total_entry)+1);if(rand+bcd140526_post_count>_vRiO.total_entry){rand=_vRiO.total_entry-bcd140526_post_count+1;}if(rand<1){rand=1;}var _vXsM=HOST+_s7IgU[159];if(bcd140526_index_label){_vXsM+=_s7IgU[160]+encodeURIComponent(bcd140526_index_label);}_vXsM+=_s7IgU[161]+bcd140526_post_count+_s7IgU[162]+rand+_s7IgU[163];_fIoT(_vXsM);}else{_fYbP(json);}}var _vXsM=HOST+_s7IgU[164];if(bcd140526_index_label){_vXsM+=_s7IgU[165]+encodeURIComponent(bcd140526_index_label);}_vXsM+=_s7IgU[166];if(bcd140526_sort_by==_s7IgU[167]){_vXsM+=_s7IgU[168];}else{_vXsM+=_s7IgU[169]+bcd140526_post_count;}_vXsM+=_s7IgU[170];_fIoT(_vXsM);

I can't paste the whole code, the website doesn't let me. But you can get it here: https://sneeit.com/blogger-random-recent-specific-label-posts-widget-all-in-one-post-feed-widget/ My settings: Post Count - 2, Post Order - Random, Specific Label - Summer, Show Thumbnail - Checked, Thumbnail Size - 200, Show Label - No, Show Comment Numbers - No, Show Date - No, Show Author Name - No, Show Readmore - No, Show Snippet - No, Show Copyright - No, Design Style - List