It just happened for me, Claymore is up to date. I've set -allcoins 1 and now mining is very 'choppy'/unstable - I see it on temperatures specially. Also now I see another thing: No new jobs were recieved for 10 mins - something went wrong with the pool
Weird, it looks like developer of Claymore wanted to avoid some forks or pools and now we have to switch to something?
BTW I'm using this setup for over two years: Windows 10 + AMD Drivers + Nanopool + Claymore