Thanks to all! Penguin, you were right to ask this question! - I always use AUTO trigger and I must have accidentally flipped a switch without thinking of it as a possible cause (oops)...
The problem is, on this machine, most of the time the status LEDs don't light during operation (they do light during power-up sequence but remain off afterward).
I sort of got used to it, but it obviously plays tricks on me and it is time I look into this issue.
Have you ever encountered this issue? A faulty register?