I am running the beta on Catalina 10.15.6, Mac mini with 4k Retina display. I have the appearance setting set to 'Auto' to change the display from light to dark mode with daylight. I have the Mac set to prevent sleep when computer is off, with power nap enabled. The machine is only turned off or rebooted if something weird happens. It has currently been up 21 days.
Beginning with Calibre Beta 4.99.13 and continuing with 4.99.14, I noticed that the first time I hit a key in the morning to wake the display, that Calibre's colors are changed so that every other row is black text on black background. I have attached a screenshot. If I highlight a black row, it shows, but then goes black again when I highlight a different row.
It isn't simply the display sleeping and waking that causes this, but something that happens overnight. The display often sleeps for a few hours during the day, but I haven't noticed the Calibre color changing then. Other operations of these beta versions seem normal.
I am not aware of anything specifically I set up to do weird stuff in the wee hours.
