Why do I get ERROR after editing an widget / segment filter?

Most of the metrics and dimensions in Google Analytics cannot be combined together in  API query, if this happens an ERROR is displayed.

Example - When when we use ADWORDS COST and User City, it will return an error.

Then, What should I do ?

To solve this you can group KPIs in different KPI  BOARDS, for the situation in above example - use a separate KPI BOARD to analyse the AdWords data.