Ooooh,
Bingo - light-bulb-on! I had stared at the pinout 20 times, and just didn't snap to the Pxy being the chip pin. (my "ID-10-T" error for the day)1. That makes the pieces all fit together. Thank you.
Yikes, so D9 is timer1A, D10 is timer1B and D11 is timer2A if I'm reading PB1,2,3 correctly. That explains why PWM on D11 was fine when using Timer1, but the other two were quite unhappy.
Keep timer1 as the pacing timer and move the 3-color LED PWM to D5, D6 and D11, and all works fine. Thanks again.
footnotes:
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- just remove the punctuation and all will be clear.