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.