Round-trip editing files from a command doesn't work anymore?

Hi,
I'm wondering if there has been a change of behaviour or perhaps a bug introduced with the local storage paths when opening files with a WinSCP custom command?

I used to be able to use my command to open files in BeyondCompare, edit and save back to the server, like a "round-trip" edit. But lately, this no longer works and I get an error dialog when I close BComp, "Copying file to remote side failed", "scp:: No such file or directory".

My command and WinSCP settings are un-changed, it worked great for years, but now it's broken for some reason. I attach screens showing my WinSCP Storage settings, the error dialog, and my custom command.

I note that if I open a file from WinSCP using Edit -> BComp (setting screen attached), it opens from a local path like:


... which is what I would expect from my Storage settings (appending session name and remote path)

However, when I select a file (or files) and run my 'diff' command, the files open from:


and so, if I edit a file in BComp, save and close, the "Copying Files to remote side failed" error appears.

Like I said, I can open files from WinSCP into any editor, BComp, VSCode, Notepad... and the path is fine and round-trip edit + save works perfectly, it's only when edit from a custom command that has the issue.

I've tried activating "Keep temporary copies of remote files in deterministic paths", but that has no affect. The docs confirm this is expected: https://winscp.net/eng/docs/ui_pref_storage

Any help in restoring this functionality would be appreciated! Thank you!