Hi Xavier,
i just finished building my PFM, every thing seems to work perfectly, but i'm experiencing the same issues Felix described.
Getting stuck notes playing it directly from my Ensoniq ESQ-1, inserting the Mutable Instruments MIDIPal into the chain doesn't fix it neither. If i hold down a chord all i hear is one note that is stuck, i can then play a second note over it or stack 3 more stuck notes above it, so it does play polyphonic but only notes that are stuck. Notes only stuck if the second note is released earlier than the first, if the first note is released first it just decays as it should, but the second won't be heard anyways.
So far the PFM seems a lot of fun if we can fix this i'm shure it'll get a lot of use
Best,
Hannes