Delta 66 omni I/O recording levels fluctutate

I am having a problem with my deltat 66 with omni I/0.  I will be recording and set a level and it will then suddenly get either lower or hotter.  (the recording input level)
  I dont know if I want to bother trying to repair it.  What are some decent interfaces in the $300 range?  I wish i would have kept my motu 8 pre