There is no difference to the files on those two archive sites, in terms of the Level 9 games, so if the files are the issue then that’s not going to solve things.
I’m not familiar with L9cut… but it might be relevant that the games that were listed (The Archers and the Adrian Mole series) are not traditional text adventures with a parser. They are multiple choice games.
I just tried quickly with the .Z80 snapshot of the first part of The Archers, and the file on that site does seem corrupted: it loaded into a Spectrum emulator, but the graphics were all messed up, and L9Cut couldn’t find game data in it.
The site does have .TZX tape images, though, which look fine. You can’t use l9cut directly on those as they are images of the data on the original magnetic cassette tape, rather than a dump of the Spectrum memory. But I loaded the .TZX tape image into a Spectrum emulator, saved out a .SNA snapshot of the memory, and l9cut was able to extract the data fine from that. So it is possible, just with a bit more work.
That they are multiple choice games rather than parser doesn’t matter in this context, the format is still the same as used by all the other Level 9 games.
I had this problem recently when testing The Secret Diary of Adrian Mole. All the z80 versions I could find online had a corrupted part 2. So I had to load the .TZX version into an emulator, play through part 1 and load part 2, then save a snapshot in SNA format.
My first attempt produced a broken SNA which the Level 9 interpreter would not accept, so I had to play through part 1 twice to finally produce a working file.
I’m not overly familiar with the ZX Spectrum and its emulators, but it might be possible to save yourself from the trouble of playing through the first part of the game. Here’s what I just tried, using the Fuse Spectrum emulator:
Start the emulator.
From the Media → Tape menu, open the .TZX image for side 1 of the game. This does not automatically start part 1.
From the Media → Tape → Browse menu, double-click on the entry named Standard Speed Data Program: "MOLE 2 "
From the Spectrum window, type LOAD "" (Actually JCtrl+PCtrl+P) and press Enter.
I think this will start part 2 of the game properly. Though I’m not sure how it deals with saved progress from earlier parts.