Assume that you have a table that has statistics on columns that correspond to a prefix of the key of the clustered or covering non-clustered index. There are some non-covering indexes for which this condition is not true. When the statistics of the table are updated automatically or manually with a specified sampling rate, a significantly smaller number of rows are sampledfrom the sampling rate than expected. This results in non-representative statistics, and inefficient query plans may be used for the queries that use the statistics.
To work around the issue, manually update the statistics together with the FULLSCAN or SAMPLE option as well as with a higher sampling rate.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.