I do not use the CCD to photograph, but the Reflex set in BULB mode.
To make Bias photos, I put the shortest exposure time,
but it is still high compared to 1/8000 of a second that the Reflex
manages to do.
The only way is to set Manual mode directly on the Reflex, but if I do this, Kstars gets stuck on the download
of the first photo.
I did some tests, even to disconnect the reflex
from the INDI Control Panel, from here select the mode
Manual and reconnect the Reflex, but I get the same result.
The only way is to disconnect everything, close Kstars, set up the
Manual mode on the Reflex and then reactivate everything,
but frankly it seems a little uncomfortable!
Am I wrong? Or is it a version bug
3.4.0 Beta 2 for Mac?
Thank you.

To take very short exposures with DSLR cameras you need to disable Force Bulb in the INDI Control Panel.

I honestly did not understand the procedure well.
I tried to disable the parameter you said,
but nothing happens.
However, I have to act on the Reflex by putting the manual mode.
But first I have to disconnect everything, otherwise Kstars crashes.
Maybe I'm wrong the procedure?