Meaning the Restore job log has a green dot and it says Warnings 0? Did you look inside the log too?
I’m not certain, but I think speed of opening a given folder depends on the folder, not neighboring ones. Sometimes it can take awhile. How big is the folder you’re trying to open? You can possibly open a tab About → Show log → Live → Profiling to see if it runs an SQL query that takes awhile to finish running. After that finishes, I think its file information goes to web browser. Is Duplicati run on the same system?
What does it say? Can you paste an image? Does About → Show log → Live → Warning see warning?
How big is the backup, and how many files does it have? In backup log, look for Source files Examined.
EDIT:
For a profiling log example from opening a subfolder of a backup of 6543 files, 7 seconds was taken at:
Jan 6, 2023 7:31 PM: ExecuteReader: SELECT “C”.“Path”, “D”.“Length”, “C”.“FilesetID” FROM (SELECT “A”.“Path”, “B”.“FilesetID” FROM “Filenames-378B2881A6AEC740929402C458D9A4DB” A, (SELECT “FilesetID”, “Timestamp” FROM “Filesets-DEB87B9A27642046BE7B33FDB8CDE37F” ORDER BY “Timestamp” DESC) B ORDER BY “A”.“Path” ASC, “B”.“Timestamp” DESC) C LEFT OUTER JOIN (SELECT “Length”, “FilesetEntry”.“FilesetID”, “File”.“Path” FROM “Blockset”, “FilesetEntry”, “File” WHERE “File”.“BlocksetID” = “Blockset”.“ID” AND “FilesetEntry”.“FileID” = “File”.“ID” AND FilesetEntry.“FilesetID” IN (SELECT DISTINCT “FilesetID” FROM “Filesets-DEB87B9A27642046BE7B33FDB8CDE37F”) ) D ON “C”.“FilesetID” = “D”.“FilesetID” AND “C”.“Path” = “D”.“Path” took 0:00:00:07.824
EDIT 2:
Basically, to find your slow spots (if they’re SQL), look for the took values and note the slowest ones.
The one I just made and found has come up before as a slow one. Google search for the first portion.
There’s also a theory that the number of versions slows it, although I suspect files are more important.
If there’s anybody around who can analyze and optimize SQL, this one might be one to take a look at.
EDIT 3:
If yours is the same, I tentatively tracked down the source, and got the same conclusion I did last time.
We’re not more expert at SQL though, so anybody who feels like they could help is much encouraged.