This appears to be due to having fields in my elastic document as dot-separated:
Reading up about this it seems that the Kibana grok debugger behaves completely differently than logstash… which is exactly opposite what you want from a debugging tool?
My patterns are using e.g.:
syntax which gives the correct (nested values) result in the grok debugger, but a single dot-separated field name with logstash.
The bracket patterns in kibana: