Troubleshooting `InternalPreventSleep`
As for the Wake up 

Check your Bluetooth settings for Wake



also for the WiFi wake
 

both in your system preferences 

then run the pmset -g cap in Terminal to see what is going on

followed by

You can inspect current settings using

pmset -g


Finally run log show --style syslog | fgrep "Wake reason" 
to see specifically who woke it up.
let it finish loading last 4 weeks

Then do a simple test..
under Apple logo Select 


  Sleep


, and wait 30 seconds to see if it wakes up.