Regarding the WMI provider and SQL Server messages:
It’s too bad nothing helpful is coming in log. The live log seems to sometimes miss log lines though.
If it’s still using CPU of roughly one core plus possible OS overhead from any I/O that SQLite wants,
Task Manager has an I/O reads (and similar) columns you can enable to see if anything’s happening.
Sysinternals Process Explorer gives a better view, but it’s probably not installed on system currently.
Sysinternals Process Monitor can show what files Duplicati is accessing (if it’s accessing files now).
Commonly when a backup gets too big for its blocksize, SQLite gets very busy accessing its files. Sometimes adding SQLite cache helps, but it’s done by an environment variable, so a little awkward.