$ koji write-signed-rpm 352c64e5 copr-cli-1.66-1.el7

Should solve the issue, I will let @parasense to take care of it

is there any way to prevent packages in tags to not get garbage collected?

Yes Dustymade.

Koji hub policy directives could be enhanced.
For example the GC policy could be set to wait longer to trigger GC. or to avoid GC when the build exists in pending tag (presumably for long time).

Another idea would be to run the routines to write out signed when an items exists in pending tag.

Yes Dustymade.
Koji hub policy directives could be enhanced.
For example the GC policy could be set to wait longer to trigger GC. or to avoid GC when the build exists in pending tag (presumably for long time).
Another idea would be to run the routines to write out signed when an items exists in pending tag.

+1