Error Uploading Json File

Hi guys! I am facing this issue when I try to upload a json template file I created from my staging site. When I try to import that file from template dashboard, I get redirected to /admin-ajax.php with a?Bad gateway?error code?502. I tried creating a new page and upload the file from elementor edit window:?Import template to your library?but I get an error too (An error occurred,?try again).

I got this log data, hope it might help? Should elementor plugin be causing the issue?

Attempt to read property “labels” on null

Line : 694

/var/www/wptbox/wp-content/plugins/elementor/app/modules/import-export/module.php

I appreciate your help.