Bucket Script doesn't allow to choose any variable

Hi,
I’m trying to use Bucket Script with Elasticsearch datasource, but it doesn’t allow to choose any variable - Variable fileds are empty, when I trying to place something there - it disappears…

The same with Derivative and Moving Average…

Grafana v6.2.5 (tried also 6.3.0 beta 2), Elasticsearch v.7.1.

As I remember, this worked for me in previous Grafana 6.1.4!!!