The time in between when Mike leaves and Carlino reappears is too long. Mike and Carlino chat with each other quickly about a strategy, and Carlino leaves. In this time, Susy has already changed, cleaned up, found the doll, and conjured up a plan with Gloria. If Carlino was supposed get there right after his conversation with Mike, Susy wouldn't have had the time to do all these things. Furthermore, it seems that he looks through the window after some time, even though he is supposed to be visiting Susy.
When Suzy sends Carlino to check the back windows for broken glass he makes a mess with the blinds (parts open, part closed etc.). The camera from the living room immediately shows the blinds smooth again. Move into the bedroom and the blinds are a mess, as he left them. When he comes back out of the bathroom, they speak for a moment. The next shot is from the living room, which shows the blinds miraculously smooth once again.
Carrying an armful of clothes Suzy rushes to the apartment door, dropping the clothes on the stairs in her haste.
Seconds later several people go up and down the stairs and the clothes have disappeared.
Susy demonstrates excellent hearing and observation skills: she can tell when people are in her apartment, notices Carlino dusting for prints, people fiddling with the blinds, Roat's squeaky shoes, etc. However, she does not appear to notice the rotary-dial mismatch between the telephone number Mike Tallman says he's calling and the number he actually dials. It's easy to tell what number is being dialed if you listen and count the number of clicks.
In the final confrontation between Susy and Roat, Roat inches across the floor with the knife slowly, and hasn't gotten off the circular carpet. In the immediate next shot, he not only has started to inch off the carpet, but has also had a shift in his position. In the next shot after that, Roat is still on the carpet and back to the first position he was in.
When Susie puts the lamp that she had knocked off the table with her cane back on the table, it rolls off the table. After smashing all the light bulbs, she returns to get her cane, but the lamp is on the table.
In the final sequence when Roat jumps out at Susy, Roat's legs hit the ground and Susy stops running and shakes her fists. In the very next shot, however, Roat's legs have not yet reached the ground and Susy is still running, and her hand motions are different.
When Susy reappears after hiding behind the refrigerator, she accidentally hits the cabinet, which has somehow fallen to the side. A second after this occurs, Roat's foot moves, as does the plate that it is perched on top of. Obviously this could not be possible if Roat has died.