In the scene where Sikh soldiers are charging to take the trench none of the soldiers reload their rifles and keep on firing numerous shots.
Sajjan Singh and Bachittar Singh turban styles are quite modern and not similar to the ones worn by Sikhs in the 1914s.
When Sajjan Singh goes to enlist at Lahore Division for the first time, 2 Sikh soldiers are shown to be wearing Patkas to cover their head. This movie takes place in 1914 and Patkas were not worn then.
In the 1914s, most Sikh men did not trim their beards while the troops wearing patkas have close cut trim beards.
While war in Britian, when Sikh soldiers are passing through the destroyed town. None of soldier have shadow while other objects have.