Install issue with brand new Fire Cube TV 3 whe trying to play iso files



Hello there!

I have just bought a Fire TV Cube 3 and I immediately installed the latest version of Kodi, following the method usually recommended online (use the Downloader app, authorise it in Dev mode, download 32-bit Kodi). 
Before I left for Japan, I ripped all my DVDs and BDs in iso format (my biggest mistake, maybe, but I wanted perfect rips) on a NAS. I then download the movies by accessing the NAS remotely, and transfer the files to a USB flash drive. I had a cheap no-brand Android media player, but the results were subpar, and the Kodi distribution was not even official, or so it seems, being labelled “KD player” (though it was Kodi through and through, which I obviously recognised qine I had already used it on PC). Playback was often shoddy, so I decided to upgrade to a modern “branded” player. Ideally, I would have liked an Nvidia Shield TV Pro, but it is not distributed in Japan, so I went for the Fire Cube 3.

It seems that the install went fine: Kodi 21 is in the app list, access to content has been authorised, it launches, it finds the USB flash drive, the iso files as well, but when I select and open an iso file, Kodi closes immediately and I am sent back to the app list.
Both flash drives I tested are formatted in NTFS format and the files play like a charm on PC.

I unistalled Kodi on the Fire Cube TV, reinstalled it, to no avail.

Have I missed something? Is there anything else I should have done? I’m at a loss, et the moment, so thanks to anyone who can help me out of my misery!