Well that is my issue , the teleworker wasn't home , the only device that was plugged is a Cisco phone 7945. No unsual traffic was detected and it is not a ISP issue in that case.
After the reboot it's back to 20ms and probably that this weekend it will climb back to 1000ms and I will have to reboot it.
We have a few ( 5-10 on 2000 ) that have this behavior. Really weird.
Support didn't find anything unusual on the MX.