Yep, ethermine stale shares went from 1-2% to 8-12% , at the moment i have 3 % staoe shares. Could we ask ethermine if there is any reason for that? will see how it will stay...
The reason for that is that the pool difficulty @ Ethermine is set to low. Then the chance of you finding a share someone else found are higher.
A simple raise of difficulty would help here. The difficulty @ nanopool has been set higher, so you see less, or no stales there.