Hey, I think I noticed this begin to happen with the latest macOS update. After a while of having Safari open I'll notice that Userscripts just stops working -- no scripts are being injected and the developer console doesn't show any Userscripts activity either. Clicking on the Userscripts extension icon in my Safari toolbar also just gives me the endless spinning loading circle. The only thing that seems to fix it is restarting Safari again. I've experienced this on both the App Store release version as well as the latest TestFlight beta version. Let me know if there's any more information I can provide.

System Information:

macOS or iOS version: macOS Monterey 12.3.1
Userscripts version: 4/1/7 (47)
Safari version: 15.4
Is this issue related to script injection? Yes