Enemy found & killed, timer at 00:00 but walkers keep spawning

In my last battle of the day Sunday 12/30, I had found the enemy camp, killed them all and the battle timer had run down to 0, but the battle did not exit and the walkers kept spawning. After killing a total of 79, I figured it had to be a bug of some kind, so I chose to flee, at which point the battle exited after choosing a survivor to be damaged as normally happens when you choose to flee, and the final battle calculations proceeded. Possible bug?