Why don't I see the same metric when I select 'Weekly' from the drop-down list in Daily Sales?
The Daily/Weekly/Monthly drop-down list is used to select another Measurement Interval for viewing. The contents of this drop-down list are determined by the Measure of the Element being viewed. When you select a different Measurement Interval from the list, Metric Insights displays an element that 1) has the appropriate Measurement Interval; and 2) shares the same Measure as the element that you're currently viewing. To ensure that you see the correct element, you will need to create a distinct Measure for each KPI that you plan to track in Metric Insights.
When you switch from Daily to Weekly, Metric Insights displays another metric that shares the same Measure. That's the only way we are able to connect them. (Sharing similar names works for humans but not for computers.) In this case, there are multiple metrics that share the same 'Sales' Measure. That creates ambiguity and leads to the problem that you encountered.
The solution is create a new Measure, i.e., 'Lost Sales'. Use that as the Measure for Daily Lost Sales at Weekly Lost Sales. That will eliminate the ambiguity and solve the problem.
In general, you will want to create a distinct Measure for each KPI that you plan to track in Metric Insights.