I have encountered an unexpected difference in how the Filter function works in QGIS 3.2 to previous versions (2.14 for example).
As a result, in QGIS 3.2 selecting an individual feature selected all the features in the filtered dataset (it appears to treat the filtered data as a single feature). In QGIS 2.14, I am able to select individual features from the filtered dataset.
I was able to get round this by using Select by Expression in this case, however, I use the Filter function a lot and would like to know if this is a known issue? and has the function of the Filter function been intentionally changed?
ETA: I have investigated this further in QGIS 3.2 and split the original shapefile into single parts (Multi-part to single parts). This affected ~150 of the 380000 features. I then re-filtered the data but observed the same behaviour as above. In the full dataset, individual features can be selected.
ETA the expression used to filter: "AttributeName" = 'TextValue' This expression worked using Select by Expression.