so, if you take your camera: try pressing the shutter when it’s facing a ceiling light (on, of course) or any bright light. you’ll likely notice that the camera spits the photo out immediately, but in the video you have shown, the camera’s light meter (the little circle to the left of the lens) is facing a table, indoors. the camera is trying to do a long exposure to compensate for the film’s low ISO. These cameras and the film they use crave light, so you’re going to have incredibly long exposure times if you’re indoors and not using a flash. The camera is not spitting the photo out because the shutter is open and the camera is mid taking a photo.

Edit: just rewatched the video that might not be the problem? but also what i’ve found is that a firm press on the shutter can help the camera shoot better. I could be entirely wrong for this whole comment, but good luck nevertheless