There are three glaring mistakes in this movie- and countless small ones.
1. Clifton Webb is told at the beginning of the movie that he cannot buy a ticket on the ship as she is completely full. Wrong- the Titanic only ran about two thirds full when she sailed.
2. During the evening before the ship hits the iceburg, the Captain is seen on the bridge discussing conditions with his officers. He turns to one and asks what the weather is like. The other one answers. The Captain looks surprized as if he didn't expect HIM to answer.
3. The watertight doors on the ship are shown to slide closed, when in fact they closed vertically.
One last thing. The case for the VHS tape for this movie shows Barbara Stanwyck standing both in the foreground and background at the same time.