Silly question: Is this for inbound calls? Outbound calls? Campaign autodialed outbound calls are controlled by the campaign settings, whereas inbound calls are controlled by the Ingroup settings. Not saying you're not "with it", but you are a bit light on the technical details of the situation.
Have you tried this in a controlled environment? (Fresh campaign, single call, ratio dialing with 1:1 and a single agent logged in JUST for testing to a cell phone YOU control to be sure you control all aspects of the call and can watch what happens with NO OTHER calls happening ...)
Also: Is this a recent development on an old machine/system ... or is this a fresh install that has never been used until now ... or (my favorite) a fresh install with an old database in it?
Also: Verify that your asterisk version in Admin->Servers matches your asterisk version from "asterisk -V" (I was unaware 1.8.24 was installed via 5.0.3, I thought it was 1.8.23.0-vici ?)
Good job posting your system specs, though. Like to see that. Happy Hunting!