Deliberate mistake: Considering the position of the surveillance camera (height and angle - almost parallel to the side of the building as well as to the sidewalk), plus the lens being indented within the outer frame, it would not have been able to capture a view of Redd on the sidewalk below like it did. (00:24:40)
Factual error: Twice during the movie, streetlights are visible: once when lady Russell informs Anne of Wentworth's engagements, and once while Anne is running after Wentworth. (Streetlights, lit by gas, were indeed conceived during the regency period - but they were experimental curiosities, and certainly not yet installed nationwide).
Continuity mistake: After Art yells for Jesse to come to eat lunch, the stick of butter on the plate is roughly parallel to the edge of the table, but is diagonal when Art and Jess come to the table. A later view from the other end of the table shows the stick of butter parallel to the edge again. Some of the family members take a roll out of the basket, but none take any butter (so did not move it). (00:20:45)
Plot hole: After sending the offensive message to his students, Charlie got on-line with them (within hours or the same day?) and said, "Well, your complaints have been heard. I've been replaced..." IF an on-line college instructor could be terminated and replaced as quickly as Charlie was, it would follow that he would no longer be able to access the on-line course to communicate with the students like he did. (01:39:55)
Suggested correction: I think this is based on too much assumption. Any sort-of ban would likely be entire dependent on whatever system they're using for their online class. And it's entirely plausible he'd still be able to access his account mere hours later, even if the call has already been made to replace him.
I worked for the Defence department in Australia and it was a running gag that eighteen months after I had left my online access to my account was still open, allowing me access to highly classified documentation, including emails. Mistakes happen.
Factual error: At the end of the film a character is walking through a studio lot in 1952. Through the trees behind him can be seen a section of a poster advertising Jackass Forever (2022).
Continuity mistake: The top of Brecken's head was close to (within a few inches of) the headboard before his mother brought the pillow. When his mother put the pillow over his face and the camera shifted to a right-side rear view, the upper part of the bed was raised about 45°. When Lang Dotrice (Brecken's father) arrived and sat on his bed, the pillow used to smother Brecken was at least a foot away from the headboard and Brecken's head (still under the pillow) was about a yard away from the headboard. (00:04:05 - 00:07:16)
Factual error: The Artist lit a match and candle in his cell. Both are contraband in prison (especially for someone scheduled to be executed). Matches pose a risk of fire/arson and deliberate burning injury or death to a person. Candle wax can be used to prevent cell and other prison doors from locking, creating an escape risk. Also, The Artist's prison cell appeared to be much bigger than a master bedroom (standard size 14'x16'). Prison cells are around 6'x8' or 7'x12'. (01:17:45)
Continuity mistake: Banker Mr. Anderson picks up his glasses from the desk and holds them near his face, then picks them up a second time. (00:51:35)
Continuity mistake: Inside the building, Nina is at different distances from the man on the bench, ranging from about one body's width to a few widths away (while accounting for her limited movement). (00:15:15)