Power management not working as expected (Ubuntu 20.04)

Desktop computer, Ubuntu 20.04, Nvidia 440 proprietary driver.

I set my power management via "settings" to turn my monitor off after 8mins and make my computer go on sleep after 1hour.

Issue:

Those parameters are not always working. Sometimes it works as expected, sometimes my monitor / desktop doesn't turn off at all and keep being awake.

I tried to isolate the issue as much as possible but I cleared off all scenarios. Example: I was thinking first that maybe an app in a background was forcing my desktop to keep awake. I only have 2 apps in background, Chromium and Discord. I tried to do as much combination as possible but actually the issue occurs in whatever scenario ( apps turn off, no discord in background, discord in background ect... ) again, sometimes it goes on sleep, sometimes it just keeps awake for hours ..

My issue is that from a Terminal perspective I don't really know where to look at ? Is there any settings that I could force to apply those settings no matter what ?

Thank you!

Vincent.