I don't know if it is because of the new vscode language client, but there is a major bug with definition for user tag. To reproduce the problem, do Ctrl+Click on an user tag in qute template without click on it (to avoid opening the file)

And you will see in the trace an infinite of didOpen, didClose of the user tag file name, which report a lot of diagnostics (because diagnostics is done on didOpen).
To stop those didOpen/didClose, you need to open the user tag file name.
I don't know if it is because of the new vscode language client, but there is a major bug with definition for user tag. To reproduce the problem, do Ctrl+Click on an user tag in qute template without click on it (to avoid opening the file)
And you will see in the trace an infinite of didOpen, didClose of the user tag file name, which report a lot of diagnostics (because diagnostics is done on didOpen).
To stop those didOpen/didClose, you need to open the user tag file name.