As a gun owner, it is not the gun, musket or flintlock that is the problem, but the quallity of the powder that is used.
If a gun, flintlock or musket were to malfuntion as often as these are scripted to, there would be a serious fracture of the barrel and or firing chamber.
It would misfire, but it would also take your face and hands with it.
The musket was made popular because of 2 reasons, better casting of the metal in it, and better refining of the powder it used. What that translates to is simple, it became reliable, dependable and could be learned in little time to great effectiveness. That doesn't meen there wasn't problems with it, but it also doesn't translate into a 1 in 5 chance of it actually working.