May i ask what kind of contracts you have purchased? And how long they are running now? I got 10MH 3mo Contracts and until now had no big problems except 24h inactive and unstable hashrate since 33 days (oldest one).

I did Mine on external Pool with scrypt contract.
But only with scrypt, with Sha256 it wasnt possible.
With scrypt i mined on ghash.io with very bad hashrate and low share accepting (<50%)