I just checked and the installer does ask for the last disk, but none of the previous disk. The game is pretty easy to manually install. Just copy the contents of all disks to the installation folder, starting with disk1. Allow it to overwrite any files from previous disks. After all files/folders have been copied, run INSTALL.EXE in the installation folder in DOSBox to setup the hardware to be used. Start the game START.EXE.

So it seems the original installer is faulty for this game?

Unfortunately the game version I got from eBay used game disks clearly copied from the original disks, so I'm not sure if they are even complete.

Mine are original (5.25"), so yeah, there seems to be something incompatible about the installer.

Just a followup, to confirm the game disks were at fault in my case, they were definitely not the original disks.

I bought another version of the game, which includes three 3.5" disks and two 5.25" disks. The installer (from 3.5" disks) works fine, the files from the first two disks are installed, and the third disk is a bonus for Tandy systems.

Sounds like they used a different installer fro the 3.5" disks.