Out of curiosity do you have a USB MIDI converter?
If so I’d be curious to know if the same problem occurs when you have the QN driving the ES indirectly via an intermediate pair of midi interfaces. I’m wondering if the QN generates more midi data than the ES can process (with the current timer configuration).
Given that you say you have to re flash the ES in order to get it working I’m also wondering if it is possible that the last note priority queue is overflowing and somehow corrupting memory.
As I mentioned in another thread if you could record a few seconds of midi data which would typically lockup the ES and send it to me (pm here is fine) I can try to reproduce the problem (and fix it if I can reproduce it).