Weird. It was not only me, at least. Both the lack of mobs and the loop on wave 3 have happened to me.
By the way, one question...the relic weapons have the attack/hp skill, but also a skill level for the special skill for the Soul. What exactly does that?
As an update, I set the quest aside til I got home, and tried it on my PC instead of my phone. Wave 3 loaded all 3 mobs per normal, and I was able to finish it. Were the other failures on phones as well?
Nope, same on PC. Last 5 mins or so of the gem quest were working normally again (mostly).