After a one-year break with Kstars, I come back with this problem of dark frames on the guiding sensor of Sbig cameras (a ST-10 for me).
I now use the 3.5.5 version of Kstars on Mac OS X 10.14.5 (my devices are attached to a brand new Stellarmate), the problem has evolved in the sense that it seems impossible at all to take a dark frame for the guiding sensor. I mean, when I tick the "dark" box in the guide panel, and make a capture, Ekos tells me that it cannot find a suitable dark frame, and invites me to use the wizard tool in the capture panel. But in this wizard tool the menu only proposes the main sensor... Even when I change it by hand in the main capture menu to the guiding chip, darks of the main sensor are taken. By the way, in a wrong directory (/private/var/folders/fd/9fwt29xd2yjbl5r55tpvjb200000gp/T/1642232941/sequence_1 and not Library/Application Support/kstars/darks), see screen capture.
Guiding without a dark frame is of course possible, but this is somewhat puzzling. Any ideas ? I also occasionally guide with a Zwo174MM, without issues (darks are well taken and subtracted).