I’m having the same problem except my library (local and Qobuz) is a whole lot smaller than yours. I’m new to Roon (still in my trial) and don’t have any backups to try that line of troubleshooting but I’ve done all the other troubleshooting (clear cache, reboot core, log out of qobuz, etc.). From Roon I’m able to search and play from Qobuz just fine.