That's it, I'm playing on a Forge Server, with some friends and two of them are using the origin, the told me it wasn't working properly and iI changed my origin to test it and worked for me. After some testing we discovered it only works if you are a server operator.

origins plus plus version 1.7.1

• Slow falling not applying
• Nether mobs targeting player

In server.properties, what is function-permission-level set to?

It's set to 2, I guess it's the default I didn't touch it, should I?
Update: I changed it to 4, still doesn't work.
Update 2: They(my friends) told me to also test changing it to 0, it broke another origin that was working fine, I changed it to 2 again and I'm not touvhing it unless you tell me to.

I'm pretty sure that mob targeting is broken on Forge. If that's the case, there isn't anything I can do. As for the slow falling, I don't seem to have that issue - I'll look some more though