I know this isn't helpful, but:
I've never had a synth (digital or analog) where external sync kept the internal Arpeggiator locked to the beat of the master machine for more than 1 minute. Most recently I had a MiniNova and and Electribe EMX and Ableton Live. Arps did not stay on beat.
When you hit a note on the Mini, the arp starts looping its pattern at key-down, not quantized to a grid, and it is not corrected for drift, jitter, and other timing differences. It's not snapping the notes to a timecode or grid. It's refererening the tempo, which is set by itself or by incoming MIDI clock signal. (Which is not a code that says 120bpm, they are little blips that have to be listened to for frequency)
The milisecond discrepancies start to add up. After a little while you can drift a full beat away.
A good arp and clock implementation can be pretty tight for a while, but I wouldn't trust it past a few minutes.
If I wanted a pattern on the Minibrute locked to, say, a drum pattern coming out of Ableton Live or a hardware sequencer, I would send the Minibrute a looping MIDI sequence out of Live or the sequencer. It could even sound like a typical arp pattern. Then every note will happen on time compared to the reference and it can't get ahead or behind.
I think of the arpeggiator as a standalone thing.