Doepfer

I just bought a Dark Time (from EMIS), which is great, but in the
manual it says to press the Step button once to go into step mode then
each repeated press of the Step button should advance the sequence by
one step, but this doesn't work on.

If the Dark Time in play mode & I press Step then the selected step
keeps on repeating at the set tempo and advances to the next step with
each press of the Step button, but having the note repeating endlessly
is really irritating.

Am I doing something wrong or might there be a fault with the Step
setting on my Dark Time?