Plot hole: Richard eventually manages to travel back in time by removing all the modern items from his room. But what about the spotlights above his bed? (00:31:40)
Plot hole: Lois and a friend of hers are watching Non and Superman fight. But this is totally senseless, because Superman had been flying around Metropolis and chances are slim that he appears in the very same spot to let Lois watch him. And, second and most important, should any doubts arise, the panning angles of the camera never show Lois's building, with the big broken window and the flag poles.
Plot hole: The film takes place around 1980, i.e. when it was filmed. But Steve Railsback appears too young for the Vietnam veteran he is playing, and in any case he has meant to have come back from the war, immediately committed a crime, and been on the run since. This would only be possible if he had been on the run for a decade, with the police in hot pursuit for all this time: that is extremely unlikely. These inconsistencies are actually a reflection of the fact that the film was scripted a decade before it was shot.
Suggested correction: Cameron is not too young for the timeline of the film. Steve Railsbeck was born in 1945. The first US troops arrived in Vietnam in 1965. If Cameron did a one year tour of duty between 1965 when he was 20 and 1969 when he was 24, that gives him a year to be discharged, return to the USA, commit a crime, and be on the run for ten years or more by 1980. Wikipedia lists 120 criminals who have been on the run since 1970 - and that's just the famous ones.
Plot hole: Antoinette Lilly makes headlines as being murdered and her husband is charged and sent to a criminal asylum...despite the fact that no body has been found and no one has even bothered to go to the hotel or town she was last at to investigate whether or not she's alive or dead. Not believable.
Suggested correction: John was framed by Antoinette's step-mother (who stood to gain Antoinette's inheritance). People have been arrested for murder without a body being discovered first though. Additionally, we find out that the lawyer who helped framed John also paid him to confess to the crime and admitted to being mentally unstable. So nobody was even trying to look for Antoinette.