I was upgrading a customer's website this evening, in a test environment thankfully, and ran into a problem. The upgrade appeared to run successfully, minus one little issue with a primary key (in the 6.0.0 script).
But after running the upgrade, the website wouldn't load. I kept getting an error in Chrome, and then finally started getting 503 errors as the server shut down the application pool completely.
After doing a little digging I was able to track down an issue in the Windows Event Viewer where the application was erroring on a problem with the LuceneNet DLL, that pointed towards the Xepient OpenSearch module, so for now, to get the site up and running I turned off the Scheduled task in the SCHEDULE table for that module. You can use the SQL below if you want to disable your own task.
USE AT YOUR OWN RISK
update Schedule
set Enabled = 0
where TypeFullName = 'XepientSolutions.XSSearchSpider.XSSearchSpider, XepientSolutions.XSSearchSpider'
This obviously will cause search issues, but for now I am just testing things out and I will figure out how I will address search before the site upgrade actually launches in production.