No assets showing via Redactor until bucket selected

Hey folks, having problems with a Perch Runway site - assets do not show via the Redactor pop-up: https://jmp.sh/9QYBL3u

If you browse to buckets, then select a bucket, the interface then works as expected.

Assets show fine in the Assets section of the admin.

I have tried adding define('PERCH_DEFAULT_BUCKET','default'); but this hasn't helped.

Any ideas? Thanks

Perch Runway: 3.0.10, PHP: 7.0.26, MySQL: 10.0.31-MariaDB, with PDO
Server OS: Linux, litespeed
Installed apps: content (3.0.10), assets (3.0.10), categories (3.0.10)
App runtimes: <?php $apps_list = array( 'content', 'categories', );
PERCH_LOGINPATH: /perch
PERCH_PATH: /home/floating/_domains/blended.iamkeir.com/perch
PERCH_CORE: /home/floating/_domains/blended.iamkeir.com/perch/core
PERCH_RESFILEPATH: /home/floating/_domains/blended.iamkeir.com/perch/resources
Image manipulation: GD
PHP limits: Max upload 128M, Max POST 128M, Memory: 512M, Total max file upload: 128M
F1: 3b606135b33e6a102526838f4152a807
Resource folder writeable: Yes
HTTP_HOST: blended.iamkeir.com
DOCUMENT_ROOT: /home/floating/_domains/blended.iamkeir.com
REQUEST_URI: /perch/core/settings/diagnostics/
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php