Import fails

When attempting to import custom post types from a JSON file that has been exported from CPT UI, the Secure Custom Fields import tool fails with the following error:

PHP Warning:  Undefined array key "key" in /home/sandbox/public_html/wp-content/plugins/secure-custom-fields/includes/admin/tools/class-acf-admin-tool-import.php on line 187

PHP Warning:  Undefined array key "key" in /home/sandbox/public_html/wp-content/plugins/secure-custom-fields/includes/admin/tools/class-acf-admin-tool-import.php on line 188

PHP Fatal error:  Uncaught TypeError: Illegal offset type in isset or empty in /home/sandbox/public_html/wp-content/plugins/secure-custom-fields/includes/acf-utility-functions.php:37

Stack trace:

#0 /home/sandbox/public_html/wp-content/plugins/secure-custom-fields/includes/acf-internal-post-type-functions.php(26): acf_get_instance()

#1 /home/sandbox/public_html/wp-content/plugins/secure-custom-fields/includes/acf-internal-post-type-functions.php(75): acf_get_internal_post_type_instance()

#2 /home/sandbox/public_html/wp-content/plugins/secure-custom-fields/includes/admin/tools/class-acf-admin-tool-import.php(188): acf_get_internal_post_type_post()

#3 /home/sandbox/public_html/wp-content/plugins/secure-custom-fields/includes/admin/admin-tools.php(191): ACF_Admin_Tool_Import->submit()

#4 /home/sandbox/public_html/wp-content/plugins/secure-custom-fields/includes/admin/admin-tools.php(134): acf_admin_tools->check_submit()

#5 /home/sandbox/public_html/wp-includes/class-wp-hook.php(324): acf_admin_tools->load()

#6 /home/sandbox/public_html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()

#7 /home/sandbox/public_html/wp-includes/plugin.php(517): WP_Hook->do_action()

#8 /home/sandbox/public_html/wp-admin/admin.php(237): do_action()

#9 /home/sandbox/public_html/wp-admin/edit.php(10): require_once('/home/sandbox/pu...')

#10 {main}

  thrown in /home/sandbox/public_html/wp-content/plugins/secure-custom-fields/includes/acf-utility-functions.php on line 37