I have the same issue.
Does ethermine pay stale shares? Nanopool says it pays for stale shares if they could produce an uncle. Unfortunately, nanopool doesn't show the stale/reject shares statistic.
Hi I have same issue I have 2-7% stale and I am pretty sure they dont pay you nothing for stale shares. It sucks I am thinking about switching pool because with those stale shares I lose about 5% more than before fork on same pool.