Negative, the mortars had sent at least 1 round each, and then they suddenly began to stop.
@Codreanu
I did notice that 2 of my targets were blocked by smoke early on. One of those two was a linear smoke fire which ended up in the same exact position as my opponent's smoke fire. So that one was kinda blocked, but would have been blocked by itself anyway. Weird. The other of the two was definitely blocked by my opponents smoke.
I had a third mortar whose spotter had good LOS to the target but stopped firing after 3 rounds. And the fourth mortar had clear LOS as well.