Ok, a few more tests.
8 hours with the tablet without the cover. Battery only drained 2% in 8 hours, which is even better performance than the Galaxy Tab S4, even though the Lenovo's battery has 2/3 as mAh.
I put the cover back on and closed the lid. Same problem after 30 mins, the screen is on for those 30 minutes. This time, I audibly heard a vibration feedback 15 - 30 seconds after I closed the lid. So something is making the screen turn back on.
I then tried keeping it in the cover, but placing the tablet screen side down. Same problem after 30-35 minutes, the screen stays on the whole time.
I don't visibly see any reason why the screen would stay on. The screen is off when I initially close the tablet cover. I guess I could take a picture of the tablet in the case with the lid closed. To see if you can notice anything odd.
But other than that, I think the best recommendation would be to not keep it in its cover when not using the tablet, and to only use the cover when actively using the tablet and wanting to keep the tablet upright hands free. Which is going to be annoying. Or, maybe try a new case.
Also, unrelated, but I asked a question about a difference I noticed between these Lenovo and Samsung tablet here. Any suggestions would be appreciated.
https://forums.androidcentral.com/a...bration-feedback-when-typing.html#post6955844