Patzer

When Michael is talking to Charlie, he briefly stands and leans back on a cabinet in his office. The camera view shifts from close to mid shot a couple of times and Michael's position with relation to the door handles on the cabinet is noticeably different between shots even though he isn't moving.

According to the grave marker, Sandra's mother dies in 1975. Shortly thereafter, Michael telegrams Bob to reserve a church for an early May wedding and says he'll be back on Tuesday the 19th, presumably April. However, the only month in 1975 where Tuesday was on the 19th was August.

In Robertson's first trip on the paddle-wheel boat to deliver ransom money in 1959, as it takes off, a pan to the street reveals traffic nearby with contemporary (1970's) cars.

With exception of old cars, nothing in flashbacks to 1959 (hair, clothes, etc.) to remotely indicate that scenes weren't set in mid Seventies.

When Court and Elizabeth are briefly seen dancing to a conspicuous waltz soundtrack (roughly five minutes into the film), their movements and steps are nowhere near in the style of a waltz, clearly indicating that the scene was filmed to another music, with the waltz soundtrack added later.