Star Wars Republic Commando prompts for disk 1 even though it is inserted

Hi, has anyone here actually got SWRC running with Lutris?
I just installed it via the GOG installer without any (obvious) problems. But now it keeps prompting me to insert disk 1 into the tray, even though it was just installed using that same disk without problems.

What confuses me the most is how can the installer see the disk, but the game can’t?