It's normal. Because report hashrate in CWI pool very fast, and hashrate depend on shares/ diff shares. That's why some time you have very high hashrate and some time very low or your worker disappear. I have a worker 350 MH/s, some time I see 800 MH/s, some time he gone in 30 - 60s.
But don't worry, you can see average hashrate and shares on Graphs. Hashrate at the moment not reflect your real hashrate, you have to see the average hashrate at least 24h. Good luck