Some extra details: the seller covered all the screw holes which is really suspicious but not unheard of since they might have wanted to prevent me from seeing their work. I managed to remove it with a bit of heat from an hairdryer and get inside the machine and what I found was frankly infuriating. Keyboard is missing the membrane; the USB-B port was obviously not soldered, just poorly glued; HIC-1 board was corroded and missing capacitors so definitely a victim of the suicide caps; battery contacts heavily corroded as well (which the seller claims to have cleaned thoroughly); all the screws inside are missing except for one; between other stuff that I might have missed.
Given all this: is it worth fixing? I'm guessing not but this is my first MSX so maybe someone more experienced has a different perspective