Revealing mistake: The barbells rigged to go down the split rails/ramp to hit the thieves trying to break into the garage do not stay on the rails like they should yet still roll straight down. The weights on the left side of the screen get out of alignment (off-track and almost derail) right after reaching the top of the ramp. For a while, it looks like the weight is sliding on the side of the ramp and then isn't even touching the ramp. (00:59:45)
Revealing mistake: When Curtis or Catherine are driving while it is snowing (e.g, on their way to the Christmas party), there is relatively heavy snow going horizontally past the side windows but there is no indication that "snow" is falling on the windshield. Wipers can't be heard (like one would expect driving in these conditions) and there is no dimming of light inside to suggest the heavy snow is blocking some light. Also, the way the snow is accumulating around the side windows is not typical. (00:33:04)
Answer: Simple answer is because ABC Family along with Fox TV Studios produced the movie specifically for their television audience. Which is what they did for "Home Alone 4" as well. Airing original movies on a channel is a way for networks to increase ad revenue as it draws an audience to watch their movies. They wouldn't have a need (and probably not a budget) to release it in theaters.
Bishop73