Septavox midi issues

Hello, I have a Septavox and have connected it to Ableton via a usb-to-midi cable. Everything seems to work as it should, except for one thing… When I play a midi clip that’s being sent to the Septavox, some notes somtimes just don’t play. It seems pretty random, too. If I play any given clip a few times, each time, a couple of different notes just don’t trigger. Doesn’t seem to be any pattern to it. Never had any issues with this particular cable with any other device before and the Septavox itself seems to be working perfectly as usual (had it for years). Any ideas what could be causing this?

If the Ableton MIDI clip has notes of very short duration, maybe the Septavox is missing them.