The RNG at work once again: buildings.
Sometimes units in them take tons and tons of damage. Sometimes you have to barrage about a hundred times with your mortars to get the units inside out. Sometimes your flamer takes forever to bbq the units in the building. Sometimes you can fire a million riflenades and the units inside remain unaffected.
Sometimes, however, you can also fire one mortar shell and the whole building instacollapses killing all units inside. Sometimes a grenadiersquad can just run up to a maxim in a building and the maxim somehow just doesn't shoot...then the grenadiers fire a riflegrenade and the whole building instacollapses.
This stuff just makes no sense. Please. Fix.
If your flamers are not aiming directly at the units inside the building, it won't do the same damage as if they were aiming directly at them so use them wisely