When Susan climbs back into the Walker house she knocks a vase of flowers off a table. She picks the vase up and puts it back, but there are no flowers in it, nor are there any on the floor.
When Frank Shawson looks out of his window after Susan's second disappearance, the date 1847 can clearly be seen on the wall of the building. This means that it could not be on the same spot as the Walker house, which would already have been standing for 34 years in 1881.
Early in the movie, Susan is watching a video of her mother acting, but the figures on the VCR counter read "0.00.00" and do not change.
The end scene as the credits roll is supposedly a couple of years on from the main story; Robert would have grown considerably, but he doesn't look a day older.