User kolvas pointed out a problem two years back that actually persists through the entire series. There are singular episodes, as presented by the complete series DVD collection and other databases, which are split into separate listings here. I have made a complete listing below of episodes currently listed which should be one episode.

Season 2
S2E1 and E2

Season 4
S4E1 and E2

Season 5
S5E2 and E3

Season 6
S6E1 and E2
S6E7 and E8
S6E14 and E15
S6E21 and E22

Season 7
S7E1 and E2
S7E3 and E4
S7E10 and E11
S7E16 and E17

Season 8
S8E8 and E9
S8E21 and E22

Season 9
S9E1 and E2
S9E15 and E16
S9E17 and E18