Error "QLocalSocket: Remote closed"

I think I might be missing a dependency, I'm not sure at this point.

Short backstory: My old Odroid server decided that living was too much and it killed it's system drive. So I rebuilt it stronger, better, faster on an old x86 machine I had kicking around. Debian Bookworm based and still headless.

I installed YACReader from the package (added the repository, etc) then realised that I needed the server package instead. Fast forward a few days whilst I configure everything else and I add my old library with the library files intact and still working on my Windows PC over the network. I see nothing, check the port and still nothing. I scan the library and it kills the library file, gone. So I rebuild that on my Windows PC and I check for an error and install libqt5sql5-sqlite, 7zip and mercurial. More success the error has gone but I get "QLocalSocket: Remote closed" instead but at least it's not trashing my library file anymore (lesson learnt there and I have a backup).

I just don't know what I'm missing or where to find any log files to check.

QLocalSocket shouldn’t interfere with the server. Why did you need mercurial?

Honestly I have no idea, I just found an old post about compiling it and just added everything there, don't know what it does or why it was needed in the compile process and I didn't know what dependencies are needed that didn't get installed when I did the apt install.

It wasn't working when I started the thread but now it is, I had restarted it before and nothing. Then I thought I would run update-library again (after making a backup of the library folder) and suddenly everything sprang into life it worked.
I have no idea why, confused but happy.