It looks like I can't send a full NRPN dump to the PreenFM2 at full MIDI speed. It crashes about one times in five.
I'm testing this on my patch editor written for Edisyn, and when I do "randomize" (which sends a random valid patch to the PreenFM2), it'll crash hard at about that rate. If I force Edisyn to only send out NRPN once every 1ms (ugh) then the PreenFM2 doesn't appear to die. Keep in mind that MIDI is about one byte every 1/3ms. This means I have to wait for about two seconds :-( :-( to update a patch, whereas at full MIDI speed it'd be a small fraction of a second.
This looks like a buffer overflow. All told I'm sending (I believe) 227 NRPN messages, so 908 CC messages or 2724 bytes.