I just tried out the yass v4.1 script, starting before sunrise, and I'm getting some significant flicker. Every few frames it jumps from the (proper) 10 second exposure to a dark 1 second exposure. Looking at the (attached) log the Tv96 jumps from -320 to 0. Any idea why that might be happening.
I see that in the log - I'll take a look later today when I have a few minutes and get back to you here.
Update : its very strange. Columns E,F,G,H in the spreadsheet show the various exposure values the script sends to the camera. They are locked solidly at 10 second shutter time, ND filter out, ISO 400 and f2.8. Yet the shutter speed and ISO values reported back after the exposure is taken jump around when the scene is dark. They seem to stabilize as the brightness level comes up.
Off the top of my head, one possibility is that you are trying to take pictures faster than the lowest shutter speed allows - i.e. shot rate faster than 20 seconds/shot (unless you have dark frame subtraction turned off in the Canon menus - that adds another ten seconds per exposure). I'll have to check whether the shoot() function waits until the shot is completed and stored on the SD card with dark frame subtraction completed too.
What did you set the shot rate parameter to?