Some people reported this problem with some MIDI interfaces as well. Looks like sometimes they have problems with too much data on MacOS, and on Linux. Try this version, which adds a delay, which helped for some MIDI interfaces:
http://www.frank-buss.de/kerberos/kerberos-test.dmg
But it will be much slower for large files.
Maybe try a different MIDI interface. You can find it on eBay for "USB MIDI cable". But if it costs less than EUR 5, usually it is crap. Once I did test a few interfaces:
http://www.frank-buss.de/midi/index.html
There were serious bugs e.g. wrong electrical interface, like no optoisolator, which could result in bad hums for audio, or not sending full SysEx message, or totally broken, like only receiving data, but not sending data. But interfaces >= EUR 15 and with a brand name are usually good.