Just a couple months ago I had made an automatic mob farm. All had been working fine. I was getting a lot of mob drops.
When I updated to 1.13 the mob amounts went way down. It is almost to the point where the machine is worthless.
I don't think mobs are despawning.
I had passed a mesa on an excursion. After I had gone 3-4k blocks further I ended up turning back. On the way back I crossed a spot in the mesa where I didn't want to deal with spiders and zombies earlier on during the excursion. But the weird thing is though is that they were still there. It was broad daylight so that couldn't have been the problem.
IDK just want my machine to work again...
I've noticed this as an issue on our server - mobs will fail to despawn as the chunks are unloaded and remain persistent, at least at a fast enough pace where one can run or boat across water. I can even watch zombies a few chunks away in broad daylight not burning until I get closer to them.