Masonry gallery pagination 'direction'

Hi, I have a problem with Masory Gallery element (Flexible Masonry type).

1. For the sake of discussion I need you to show two types of behavior, after clicking ‘load more’ button. While gallery is loading additional space is needed, so gallery sometimes:

a. scales it self downwards: https://www.dropbox.com/s/8ebhe8b4avw39cv/down.webm?dl=0
so pagination button moves downward, content underneath is pushed down;

b. scales itself upwards: https://www.dropbox.com/s/xm15g4jdovab3ku/up.webm?dl=0
so pagination button moves downward and content on the upside is pushed upwards.

I have tried many different layouts to determine what is controlling this behavior and failed miserably, so if you could point me to some documentation which explains it it would be great.

But most important question is: can I get rid of (b.) behavior? Maybe is there some code snippet to make gallery always scroll downwards?

Setup info: fresh installation of WP (on some test domain), fresh installation of Enfold, no cache, no plugins, no customizations, etc. Latest versions.