Mobs for hearts not spawning

Doing map completion yet again for Legendary weps and I'm noticing the mobs aren't always spawning.

So far I've noticed 2 hearts with issues:Help the wupwup tribe in fireheart rise. Lowest heart on the left. The mobs weren't spawning near the truffles. I went back later and it was fine. Different IP maybe.Help sleekfur warband defend the road at soldier mesa. The mobs that attack the machine guns aren't spawning. This one I though to grab the IP 34.201.97.124

And yes I waited to see if they would spawn both times.

They can still be completed but slower going without all the means of advancement present.