Other mistake: When Tom Hanks cuts his hand and loses his temper, he picks up the volleyball with a bloody hand and throws it. When he picks it up, you can see that his fingers are spread. When you see the handprint that he makes "Wilson" with, you can see that the fingerprints are together and parallel.
Other mistake: When Noland is casually urinating into the ocean late one night we see a light on the horizon. It can only be from a passing ship. Noland doesn't react at all, and it is directly in his line of sight. He couldn't miss it.
Other mistake: In the cave we see Tom Hanks drawing an analemma without a precise timekeeper, which is needed to draw one. What he could have done is a meridian rect, which is build with the meridian time. The analemma is the differential chart between the solar time and civil time.