When I first gained an interest in the Titanic, I was somewhat younger and less observant of historical accuracy, so I tended not to notice if a work of fiction contained a historical error. At the time, I just read as many books featuring the Titanic as I could.
However, now that I'm older, as I read works of fiction set on the Titanic, I notice a lot of little things, or common errors that seem repetitive among not-fully-researched historical fictions.
Common errors I tend to come across in books:
1. Boat Launch Sequence of Events
Authors seem to like to reorder the launch sequence of the boats. Or maybe it's more that they just don't look it up and get that particular detail straight, I suppose.
But anyways, the example: Character misses boat four and is instead urged to get into boat six...which should have left a good deal earlier.
2. Passenger Shuffling Among Lifeboats
In a book I recently read, an author shuffled several passengers to different boats than they were historically rescued in in order to put their fictional character in with a particular historical passenger.
I get it a little bit, as an author...They want their character to stay on the ship until the last minute, to squeeze in as many events on board the ship/during the sinking that they can, but they also want the passenger to get in a boat with a particular historical character that they may have met/befriended earlier in the story...It still bugs me a bit though. I guess it's just a lack-of-research thing. It's small, but it seems sloppy to me.
3. Lifeboat Location
I read a book (same one from number 2) where the author had boats (identified by number) on the wrong side of the ship. Another story that I read a long while ago had the character miss one boat (an even numbered boat) and then walk further aft on the same side of the ship and get into an odd-numbered boat. Odd numbered boats should have been on the starboard side, with even boats on the port side. :/
Passengers that boarded at Cherbourg aren't going to be boarding at Southampton. And the opposite is also true. Bruce Ismay boarded at Southampton, not Cherbourg. And, from a separate book...Astor did board at Cherbourg, rather than Southampton. So your character couldn't have been having a conversation with him before noon on sailing day in Southampton.
5. Officer Watches
Some authors like to involve a particular officer in their story without paying attention to when this officer would actually be on duty. Especially with the junior officers, I've noticed this. Since I'm writing my own story, I've gone through and made a chart showing the different times each officer was on duty, which has been helpful. People might have an officer participating in some scene of their story, stating that he's there because he's "on duty" when in actuality, the officer was off duty and, likely, especially in the case of the junior officers, asleep.
I've seen others too, but can't think of them off the top of my head. The biggest issues are always with the boats. :/