Flypool hashrate deviation 4.2k to 3.7k

I’m mining at 4250 sol/s however on flypool it shows 3.7k Is this kind of deviation normal?

Yes. Through personal experience and looking through at least a dozen other mining addresses associated with Flypool, +/- 10-15% doesn’t seem to be uncommon. Flypool is showing you your effective hash rate (and effective average hash rate) which will be dependent on the number of shares submitted each round of payouts (variable in length, to some extent), which will vary with luck (your computations for a given time period will not yield the same number of accepted shares).

Obviously, taken over long periods of time, you should see a relatively stable average effective hash rate. If you don’t, that’s when I’d be concerned.