backlight goes off sometimes

I have a macbook pro.

Have bought it used from a local market.

The problem is sometimes the backlight goes off..

The issue first appeared when I closed the lid and it went to deep sleep. after I opened the lid the backlight is not working. The display is there as I have tested it with a torch pointed at the apple logo and I was able see the desktop and stuff.

After two days of no backlight I turned it on again and the backlight was working.

After a week the backlight again went off when I was working on laptop and it went like for 10 days. I kept trying to turn off and on the laptop and after 10 days it is again working.

I am not sure if it is Backlight IC issue or fuse issue.. (because in those cases it should not be working completely right ?)

Please let me know if anyone knows the possible problem and can point me to the right direction as I am not sure when will it again start to bug and may be never get back.

(I already have tried the pram reset and other reset methods defined on different topics)

The issue did not occur before upgrading the macbook to catalina so I think may be it is a software issue ? I tried to downgrade it to mojave via usb but I seems to have installed again the same catalina version (don’t know why)