The dissolve I mentioned is weird, since there's only a slight camera movement from the "before" to the "after", unlike normal dissolves where there is a complete scene change. So it's easy to mistake for a continuous shot. (Hitchcock made ROPE to look like the whole movie was a continous shot, with the reel changes masked by a cut showing the back of someone's jacket! Hitchcock never repeated this gimmick in another film. If you read about what they had to do to achieve the effect, you can tell that it just wasn't worth it. A movie that is supposed to occur in real-time, with one setting, could have been just as effective without the gimmick. I must admit, however, that when I was initially getting into Hitchcock movies about 40 years ago, reading about the gimmick made it one of the first tapes of Hitchcock I rented from the video store -- remember those?)
There are some bad edits in the movie anyway -- I think it was mentioned somewhere above. In the scene where Groucho makes the remark about living in Pittsburg, there's a cut right in the middle of the wisecrack. Though to be somewhat fair, it occurs between 2 sentences of the crack. Some of the dissolves happen with barely enough time to let the characters finish a sentence!.
Also, a weird edit right after Harpo vacuums Sig Ruman's toupee, as you see him exiting the room. It's cleaned up a bit in the HD version I've seen online.
BTW, although this film could use Margaret Dumont, at least it has Ruman! Probably the greatest male co-star the boys had.