This is caused by the code in jaupdater.php looking for a log file in the directory to check if an update has been installed. This is frankly a dumb and lazy way to check if the update script has already been executed, especially on static environments like AWS beanstalk where the filesystem is regularly refreshed.
The workaround is to add (an empty) updated_2.5.7.log file back in the administrator\components\com_jaamazons3\helpers folder.
