I just noticed something strange - logged and saw the estimated reward is very low - say 1000X less then expected and my score was low (recently reset).

Then it started to get larger but ***very slow*** like about 5 - 10 minutes estimated reward is still not back to normal. So if block is found during this time the actual reward will also be very low.

This is probably because the total pool score was not reset at all? I saw somebody already pointed that out.

This would explain how people might get low payout with bad timing, but that would not explain how others would get disproportionally large ones  

P.S. Hash rate was normal (about 1 ghash) and all workers were on - last shares 0 minutes ago.