Actually the agents are told to remove any device that emits a radio signal so they can not be located based on signal triangulation so video conferencing is logical. What isn't logical is that they are underground in a bunker within the bar yet they are using hand held radios to communicate with the agents outside the bar.
When Agent Little is shot by the woman assassin, he is hit in the right elbow. A minute later when Winnie Jones engages in a shootout with agent Little we can see that the left elbow is hit. Also the shot wound just appeared out of nowhere on the shirt the frame before he got shot when he came from under the counter.
Chicago has no mountainous terrain with essentially flat topographical features however in this movie after the bar is blown up and emergency personnel respond the camera pans between two building and you can see low mountains in the distance.
Actually, in the summertime in the northern hemisphere, the sun is in the north nearly all day. It rises in the northeast and is nearly overhead at noon (standard time) and sets in the northwest. It's in the wintertime that the sun is never in the northern sky.
When Tom Berenger's character is explaining the number significance of playing cards he states that there are: 4 suits for the seasons, 52 cards for the weeks in a year, and 365 "pips" for the days in the year. Actually, in the deck he is playing with (pips in two corners) only has 348 pips, and other decks (pips in 4 corners) have as many as 452.
When Kaitlyn Tremor places the explosive device in the fuse/disconnect box, the disconnect handle is clearly in the off position. Blowing up this box would have no effect vs. in a later scene when the device explodes and power to the bunker goes out.
When they arrive at the "safe house" the binoculars indicate North as they are pointed towards the back of the van. When agent Baker steps out of the van, the sun shines directly into the camera. The sun never shines from the North on the Northern hemisphere. Also the sun appears and reappears during this short scene.
When Walter Weed near the end of the film walked towards behind the car, it is clear visible that the car engine is running (smoke coming from the exhaust). When he seat into the car, he started the "running" engine.