Other mistake: After Jack and Rose are "done" in the cargo hold, they come out onto the bow of the ship laughing. Whilst the door they used to get onto the bow does lead to the cargo hold, inside you have to go down a flight of stairs and are greeted by a cast iron hydraulic door which can't be opened from inside the cargo hold, and would close automatically if the control wheel wasn't being held. The only way they would have been able to get out is by running back through the boiler rooms.
Revealing mistake: You need to watch carefully for this as it's tricky to spot, but it is visible without the need of slow motion. When the steward calls for the gate to be unlocked to the third class passengers, the gate is already open and just pushed to a close. You can see the gate wobbling and separating around the lock area. Also as the gate is unlocked we see a key being pressed against the lock to unlock it. However the key doesn't actually engage with the lock, making it impossible to open it. (02:02:50)
Factual error: During the sinking scene, Murdoch looks down the crew stairs on the starboard side, where water is entering from an open door on deck A. That door should have faced outward (starboard side) otherwise the door would have lead into cabin A7 and I don't think the occupant would have enjoyed that.
Factual error: In the seen after the preacher finishes his dialogue; it shows the woman floating in the first class lounge with which is completely under water. But about a minute or so later after it shows the maid slide down the deck, the part of lounge that was supposed to be flooded is still above water. The lounge in just a bit forward of the 3rd funnel on A Deck which wasn't submerged until after the break up in the film. The light fixture is one deck down aft of the compass tower between funnel 2 and 3.
Factual error: When Rose's mother is having tea, all the women are wearing gloves as they have tea. This would never have happened as Edwardian ladies always removed their gloves and placed them in their laps under their napkins when they sat at a table, before eating or drinking anything so as not to soil them.