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@Gordon
I'm afraid it happens on all of them - the extra power draw just drops the voltage enough to dim the backlight. At 3v it's not much above the voltage needed for the LED so any dip in voltage is very apparent.
A decently big capacitor on the 3.3v line would help but at the end of the day if the calculation goes on for more than a small fraction of a second you'll still see some dimming.
To be honest using the backlight on CR2032 won't be amazing - it's not as bright and the increased power draw will flatten the battery a lot more quickly than might happen otherwise.