I ran into the same problem myself, it seems to be due to the fact that grafana is truncating times to milliseconds despite the fact that they may be stored in the database at a higher precision
For example I have a series of points in my influxdb at time 1514507093.324336863, 1514507093.324621349, etc
When I zoom to this point grafana displays it square on 1514507093.324 (if you look in the query inspector you can see it is specifying ms as precision). This works down to a screenwidth of 2ms, although it incorectly groups all the points square in the middle of the screen, at 324ms:
select * from table where time >= 1514507093323ms and time <= 1514507093325ms
However when you try to zoom on the points grouped at this millisecond the query logic fails as grafana is unable to think at higher resolution
select * from table where time >= 1514507093324ms and time <= 1514507093324ms
All the points that previously appeared on the whole millisecond are suddenly excluded by the query and disappear off to the right of screen. Apart from being surprising this means you can’t inspect values occurring with separation less than a ms
It’d be nice to enable at least microsecond (preferably nano) resolution in grafana, this would solve both the behavioural and functional issues here