I was indeed able to reproduce the exact same issue:

  • Turning of the auto bulb mode
  • Keeping exposure times below 30s (25s for example)
  • Sony A7S set tu manual, 30"
Despite all of this, the Star eater DOES turn on, which indicates the body is still being used in bulb mode.
I could verify this by taking a FFT of a dark frame showing a clover pattern instead of a homogenous pattern with central dot.