Are you talking about the recent Trump/Putin summit? Because that wasn’t quite editing video footage. There actually was a mistake and a reasonable reason why part of Putin’s answer, saying he wanted Trump elected, was cut out from the transcript.
That being said, the fact that the White House hasn’t gone back to correct the official transcript is the problem.
""What happened? If you watch the videos, it’s pretty clear. At some point in the middle of that question, there’s a switch between the feed from the reporters and the feed from the translator. In the White House version of the video, you can hear the question being asked very faintly under the woman who is translating saying “president.”
If you’re wearing headphones, you can notice how the latter part of the question is suddenly audible in the right earpiece. At first, the right channel is only the translator. Mid-question, the reporter is suddenly heard in both left and right as the translator feed drops out. Notice, too, that Putin then picks up his earpiece — through which he can hear the translations — and puts it in his right ear.
Our transcript and the White House’s were apparently based on the feed that runs only in the right channel. A White House official told CNN’s Abby Phillip that its transcript “did not have Mason’s audio turned up in time,” referring to Reuters reporter Jeff Mason, who asked the question."