ipad case cover is not working sometimes

I have an ipad air 5th gen and i am using a case with a cover (not from apple) and it’s not working sometimes. Most of the times it works but there are times when i flip the case the ipad’s screen doesn’t light up and it takes a while for the screen to respond to my double tap to turn on or even when I press the lock button. Even when my ipad case doesn’t have a cover, the problem is still there. My ipad takes a while to respond to my double tap to wake and when i press the lock button. I have tried updating my ipad to the latest version and i tried 2 cases already but the problem still happens. What seems to be the problem?