That's interesting, I'll keep an eye on it and see how I get on.
My 1600X rig is currently set for SCC and MIP only and I've gotten 17k ppd for the last few days. Note that I have a mild overclock (3.8Ghz) and am running Ubuntu 17.04.
@infrared maybe your overclock is unstable or your Linux install needs an update?
Even the 1800x running stock nose dived on saturday, and the same sunday. The oc'd one was busy playing VR with mates on Saturday, but still didn't pick up after running uninterrupted on Sunday. I'll double check the stability but it's been consistent right up until I changed to MIP, and I'm not pushing the chip hard for WCG. I noticed later I was also getting tasks from Aids at home, ebola, cancer markers etc. after I changed to MIP so maybe that's why the ppd took a plunge
edit - I checked the wcg results page, there is 1 Invalid result listed for the oc'd 1800x so I'll up the voltage a notch, but it also has 675 Valid ones so I don't think this is why the points are down. Oh well, I'll keep an eye on it.