Nah, I just rechecked with a setting as fast as it goes and the encoder is acting up:

- slight movement of shaft affects other circuit,
- missing pulses on 2nd circuit.

I'll have new EC11 PCBs coming in a week (silkscreen of 1st batch is wrong - D'OH! ), I'll test a few other EC11 double-shafts then.

It's not like I'm lacking tasks and chores to do until then.