Factual error: During the battle scene the voiceover says that it is February 1915. The battle being portrayed is obviously the Second Battle of Ypres because it involves Canadian troops and it's the first time that gas was used in the war. The actual battle didn't take place until the end of April 1915.
Factual error: Bones calls the Drill Sergeant "Ma'am" or "Sir" several times and she never does anything. Anyone who has been through Army Basic Training can tell you, a Drill Sergeant will NEVER let "Sir" or "Ma'am" pass without comment. And this is not a character mistake, It would be like calling a Senator "Governor" or a Catholic preacher "Rabbi" and having them ignore it.