Bulk Edit Metadata problem

[koland]

I have a group of files that I want to add " (ARC)" at the end of the title. Finding and displaying/selecting the files to modify is easy.

When I go into Edit Metadata, then pick the "Search and Replace" tab, I have the following
Search Mode: Regex
Field: Title
Search For: (.*)
Replace:\1 (ARC)

The result, tho, is:
Original Title (ARC) (ARC)
both in the preview and the library.

I have used bulk edit before, but usually to remove series info, fix author names (that have commas), etc. This is the first time I have used it to try to add characters after the name. This seems like a major bug, but possibly one no one has run into before?

For now, I have to then run a second bulk edit on the same group, with:
(.*) (\(ARC\))
replacing with just
\1
which works, but is a bit of a pain. Am I doing something wrong? Or can Calibre be fixed?

Calibre 9.11 (was doing the same in another 9.x version, just updated to see if this had been reported and fixed).