The machine arrangement remain unclear (see my previous question, and your info that I quoted).
From what I read, you have:
source machine ↔ network share? ↔ Duplicati machine ↔ local folder
and you were suggesting Duplicati was filling the source machine, and now ask about its pagefile?
Please correct above diagram if it’s wrong, otherwise I don’t know how Duplicati is directly involved.
Duplicati’s size can only directly impact the pagefile on the system it’s on, not on a remote system.
How are you getting to the remote system anyway? Maybe reading data is making some server big.
Looking in Task Manager or opening Resource Monitor from it might show something that’s growing.
Figuring out what’s writing to disk is harder. It wouldn’t be Duplicati during backup. It only reads files.
Sysinternals Process Monitor on source machine can show writes in great detail, maybe too much.
Resource Monitor might be more useful to view what’s writing. Below is how it looks on my system:
Writing doesn’t always mean filling up space. It might mean overwriting, or deleting then recreating.
Another way to chase space fillers might be to use File Explorer’s search for recently modified files:
* datemodified:yesterday size:medium or whatever other options seem useful in Explorer UI.
Or if your source machine had nearly zero free space before, maybe growth was from pagefile.sys.
If that’s the case, then see above for Task Manager. Sort processes by commit size in UI by a click.