Our rules for Multi-Part Episodes:

"Episode (1)" "Episode (2)" should be used for regular multi-part episodes. For example, "To Be or Not to Be: Part 1" should be entered in the database as "To Be or Not to Be (1)", and "The Sound of Thunder - Pt. 1" as "The Sound of Thunder (1)."

"Episode (I)" "Episode (II)" should be used for multi-part interseries crossover episodes. In simpler words, it should be used when the storyline starts in an episode of Series A and continues in an episode of Series B.

You can read more here. I'm closing the other reports.

I have restored and locked the modified titles.