This is just cosmetic, and not completely reproducible, but...

Many times, when I open RPN for the first time and tap a numeral key, the whole key will momentarily disappear.

It doesn't happen all the time, but when it does happen, it's always the first key tapped on opening RPN, and it only happens once. I've never seen it happen again until I close RPN, and reopen it.

Regards,
Tom