Is it normal for the E paper display to flicker?
yes, it is totally normal. check any other device with epaper (amazon kindle, electronic shelf labels,…) how it is acting during redrawing.
hey Norm, yes as Randy mentioned this is how the e-ink technology works, you can read more about it here - https://support.reekon.tools/hc/en-us/articles/21075469206036-Why-does-the-E-Paper-Screen-Flash-Invert