Thank you for your hint. I had 57 pending jobs and that helped me to release the jobs out of the queue! 
There is an open ticket about the issue on GitHub and a fix in progress:
With v5.12.25-M175, I still have to run the jobs manually to get rid of the pending jobs message:
2 Likes
louwerj
23
The solution works here too. The queue is empty again. Thanks!
hzink
24
How do you prevent ‘scout’ from continuing to create these pending jobs?
I’m using v5.12.27-L174 (self hosted) but there are always pending jobs.
I can only solve it with
php artisan queue:work database --queue=scout
Is there any possibilty to fix this issue?