Miners dont run at a constant speed, that variation is normal. The reported hash rate is just an average of what the miner is doing overall.
As an example this is an s7 running at 4.050 th/s (averaging 3.98th/s pool side)
As far as the machine not reconnecting, that is not really normal. The S4s I used to run never needed any type of reset due to a lost connection, it would just pick back up where it left off.