Data not showing in query until after similar data is inserted


We have an influxdb system setup in AWS on an EC2 instance.
Version 1.6.1
8 GB RAM on the instance

We have several DBs.
One of them contains several measurements, several of which have been spawned off into their own DBs.
One of the measurements at the moment only has 936 data points.
However when I query for specific data that I know exists during specific time ranges, I get nothing returned to the query.
If I then re-insert the data with a time value that is microseconds different from the time that exists, both rows show in a query.
If I then subsequently delete the most recently inserted data point, as the time is different enough that I can do that, the original data point is now returned by a query.

Any suggestions as to what is happening, or easier ways to fix it?