No usable logs when scheduled build fails

I have two issues in my nightly scheduled build.
1.) The same commit is build every night but with different result
Why the same commit is build over and over eventhough it has already been build successfully I dont know.
Question asked here but not answered yet: How to use pipeline schedule.
2.) When it fails it fails with no logs at all.
I wonder if there is a way to log even when it fails? I have a lot of logs when goes green but not when it fails.
And please remeber that the same commit can go both green and red.

Thanks for all your help