I recently updated our Elastic instances to 7.15.2. I am seeing mixed results when applying filters in Discover. For example, when filtering out a host on the agent.hostname field (i.e. 'NOT agent.hostname: example_host), not all instances of the host are removed. If I filter for only that host (i.e. agent.hostname: example_host), the filter appears to work correctly and only show results for 'example_host'.
This appears to only affect the logs-* datastream coming from Elastic Agent instances. The agent.hostname field filters correctly on other Beats indices. I also only see this behavior on that specific field for logs-*.