Some say the DLC glitch is caused by Come Fly With Me, others say it's caused by Vault 34. The truth is it's not caused by any specific quest or location, people just think it's caused by whatever they're doing at the time it happens to them. Then rumors spread.
My first time playing through I went full-bore into the game and did Come Fly With Me as soon as it was open to me. I did the whole thing, including picking up the Spacesuit, and the next day I went to load my save and it was corrupt. I currently have a game that I have since completely restarted, played somewhat more cautiously through this time around and did Come Fly With Me again all the way through and did not pick up the Spacesuit. My game has not had any problems in regards to the DLC save corruption as I have not entered Vault 34 either. Nobody can say it's black and white, it's not that simple. While you may have gone through Come Fly With Me and picked up the Spacesuit with no issues, I have. If those were the only two test cases, that's a 50% bug right there. That's pretty big numbers when it comes to an issue like that. Spread that out over a few hundred thousand people and compare the numbers, it will look quite different. I say to prove this one way or the other, pick up the Spacesuit in a play-through; save, quit, see what happens. Try it a couple of times, and the more people that find the issue the more proof you either have for or against this argument.