When selecting specific files (not all) there is a button that pops up “Confirm File Selection” – if you press that button it makes the “Push site” button inactive and greyed out, disabling the push functionality.
I’m on Mac Intel chip.
Hello @charlie-innermedia 
Welcome to the community!
The DevKinsta has been in security & maintenance mode in terms of providing updates and I’m afraid that this bug has been in our developers’ backlog for quite some time and we don’t have an update.
While we work on this, please use a workaround.
Select any of the files from the root to be able to partially select files from wp-content. For example, what I do is I select any file from wp-content/theme/any_theme and then select robots.txt.
This should allow you to push selectively while we work on the bug.
Kind regards