From time to time some of my miners go offline, but when I log to them I see that they are still mining and accepting shares. I have to turn winminer off, and then start it again to be able to see my miner online again. Why is this happening?
BR...

After a few days the winminer became more profitable than Nicehash.
It just happens to me that the site is not seeing the rig, while mining goes.

I too have had the local machines showing that they are chugging away although in the "Live" page they aren't showing up as being online. I usually reboot when I see this occurring and it has happened more than a dozen times to me since I have signed up with their system. How much is lost or if any I can't say for certain as I believe the systems reconnect automatically after some point.
Benchmarking seems to be continuously occurring and quite often selecting a coin that is not the most profitable. The benchmarks take several minutes to complete on each coin which seems to result in lost money for the miner.
My biggest concern going forward is the speed at which the WinMiner software mining shifts from coin to the most profitable coin. When compared to Nicehash there does seem to be quite a delay in getting the rigs to push from one coin to another. Sometimes this has taken up to a minute or two which can really add up to lost cash over time.
I also believe there should be an alert system much as others have stated that allows a user to select to be notified via email if a rig is offline. I did like this feature in NiceHash and would love to see it here.
Overall I am happy with the WinMiner service. I am sure it wasn't an easy task to deal with the influx of new accounts but they dealt with it pretty well and it has been a solid easy mining alternative to Nicehash. The best part is that I have been paid out timely every time I have selected to withdraw my earned funds through Ethereum.