AWS Lookout Metrics Showing NULLS for 0 values in data

We are using AWS Lookout Metrics for anomalies detection from sometime now. While analysing we identified that it shows broken graph for some dates and while hovering the graph says value as NULL whereas the value is available in the table for that specific date. We suspect there's some gap while learning the available data or something is not correct. We are using Athena tables as data source and offset is set to 1 day.

Thanks