Having one of the following two problems?
1) Grouped views not working properly when you’ve selected a BCS / External data field as the group field
2) Column filtering not working properly for BCS / external data fields
But these problems seem to be inconsistent, some records work and others don’t? Chances might be that you’ve selected a field for which the values contain newline characters. This consistenly brings problems with grouping and filtering. The best option you’ve got is just to eliminate newlines in your datasource. Using SQL? Then this will do: REPLACE([column], CHAR(10), ‘ ‘).