TWS is constantly trying to determine whether a new hit should be associated to an existing trackfile, which implies that there's always going to be room for error and sometimes different hits might be correlated to the same track, or the opposite, hits on the same target might create separate tracks even though there's only one target present.
RWS doesn't try to correlate anything, so as long as the radar determines there's two separate hits, they'll show as such. However, targets can be so close together that they fall within the radar's resolution and so even in RWS they'll show as a single target.