Got a strange issue.

Sometimes several of my workers stops being shown their shares at My account stats whilst others shares' number continue to increase in time.
Estimated reward also drops.

Looking at workers I notice nothing significant at all - they're producing shares as usual and cgminer marks them as Accepted.

After being restarted cgminer performs as usual but now shares are being counted and I see them in stats.

Looks like there's some instability in counting of shares which were accepted by stratum.

Does anybody have the same behavior?