Had this issue for years over 2 machines.

One had some shit in the background the prevented standby.

Other was so simple it pissed me off… … the damn mouse jostling around in the laptop bag was walking it up.

I’m still going to point the finger at windows because 1) there should be a better tool for identifying what is keeping a system awake and 2) should be default for a mouse to not wake a portable machine who’s lid is shut.