Will squirts Jack with his bottle of water, the water level obviously drops quite a bit, in the bottle. But in the next shots, the bottle is filled right up to the top once again.
When Will is talking to Jack and is folding tea towels, he folds the same tea towel twice between shots.
After Will squirts his bottle of water all over Jack, the amount of water on his shirt and face differs through following shots.
When Will is playing with his new Aeron chair he accidentally hits the left side of it, causing the gas spring to lower it all the way. The gas spring release on Aeron chairs is on the right side.