Sounds like the backlight could be on the way out @redserv
I’d suggest using the CS indoors for a while and connect the HDMI-out port on the CS to your TV. If the CS goes black but the display is still visible on your TV, and the touch screen still works (even when black) then it’s definitely a backlight issue.
I speak from experience as I had the backlight on one of my CS Ultras fail a few years ago. Details here: My CrystalSky Ultra backlight finally failed 😭 (and subsequent repair)